serv1824-950h-962h.pdf

SERV1824October 2006

TECHNICAL PRESENTATION

950H AND 962H WHEEL LOADERSAND

IT62H INTEGRATED TOOLCARRIER

Service Training Meeting Guide(STMG)

GLOBAL SERVICE LEARNING

950H AND 962H WHEEL LOADERS ANDIT62H INTEGRATED TOOLCARRIER

AUDIENCE

Level II - Service personnel who understands the principles of machine system operation,diagnostic equipment, and procedures for testing and adjusting.

CONTENT

This presentation describes the location of the basic components on the engine, and theoperation of the power train, implement, steering, and brake systems for the 950H and 962HWheel Loader. This presentation may be used for self-paced and self-directed training.

OBJECTIVESAfter learning the information in this presentation, the technician will be able to:

1. Locate and identify the major components in the C7 ACERT engine, power train,implement, steering, and brake systems;

2. Explain the operation of each component in the power train, implement, steering, andbrake systems; and

3. Trace the flow of oil through the power train, implement, steering, and brake systems.

GLOBAL REFERENCES

Specalog:950H Wheel Loader AEHQ5675962H Wheel Loader AEHQ5676IT62H Integrated Toolcarrier AEHQ5677

Service Manual:950H, 962H Wheel Loader, and IT62H Integrated Toolcarrier RENR8860

Parts Manuals:Aurora Built Machines

950H PIN K5K SEBP3866962H PIN K6K SEBP3874

Gosselies Built Machines950H PIN N1A SEBP3845962H PIN N4A SEBP3846

Brazil Built Machines950H PIN M1G SEBP4274962H PIN M3G SEBP4283IT62H PIN M5G SEBP4282

Training Materials:

TIM "966G/972G Series II Wheel Loader Command Control Steering" SERV2660

The following training materials are on SERV1000 the Legacy DVD Set.

TIM "950G/962G Wheel Loader Steering and Braking" SEGV2643TIM "966G/972G Series II Wheel Loader Command Control Steering" SEGV2660TIM "950G/972G Wheel Loader Power Train" SEGV2642STMG "950G/972G Wheel Loader Introduction SESV1698

Estimated Time: 30 HoursVisuals: 209Form: SERV1824Date: 10/06

2006 Caterpillar Inc.

SERV1824 - 3 - Text Reference10/06

TABLE OF CONTENTS

INTRODUCTION ..................................................................................................................9Component Location.......................................................................................................11

ENGINE................................................................................................................................13Engine Electrical Block Diagram...................................................................................14Speed/Timing Sensors ....................................................................................................17Engine Speed/Timing Calibration Port...........................................................................18Fuel System.....................................................................................................................19Fuel Transfer Pump.........................................................................................................21Power Derate...................................................................................................................22High Fuel Filter Restriction Derates...............................................................................25Engine Inlet Air System..................................................................................................27Turbo Inlet Pressure Sensor............................................................................................29Air Inlet Restriction Derate ............................................................................................30Engine Oil Pressure Sensor ............................................................................................31Low Oil Pressure Derate.................................................................................................32Engine Coolant Temperature Sensor ..............................................................................33High Coolant Temperature Derate..................................................................................34Intake Manifold Sensors .................................................................................................35Intake Manifold Air Temperature Sensor Derate ..........................................................37Virtual Exhaust Temperature Derate ..............................................................................38Engine Idle Management System (EIMS)......................................................................44

POWER TRAIN ...................................................................................................................46Power Train Electrical System .......................................................................................47Engine Start Switch and Diagnostic Service Tool Connector ........................................52Transmission Shift Lever................................................................................................53Transmission Shift Control .............................................................................................54Transmission Oil Temperature Sensor............................................................................61Left Brake Pedal Position Sensor ...................................................................................62Implement Pod Downshift Switch and Remote F-N-R Switch .....................................63Parking Brake Pressure Switch.......................................................................................64Back-up Alarm................................................................................................................67Warning Panel - Left Side ..............................................................................................68Implement Control Valve - with Ride Control ...............................................................69Secondary Steering Intermediate Relay..........................................................................70Engine Start Relay ..........................................................................................................71Transmission Hydraulic System - NEUTRAL...............................................................72Transmission Modulating Valve - NO COMMANDED SIGNAL ................................80Transmission Modulating Valve - COMMANDED SIGNAL BELOW MAXIMUM ..81Transmission Modulating Valve - COMMANDED SIGNAL AT MAXIMUM............83Transmission Modulating Valve - Solenoids..................................................................85Transmission Relief Valve ..............................................................................................87Remote Pressure Taps.....................................................................................................91


TABLE OF CONTENTS (continued)

Variable Shift Control .....................................................................................................93Integrated Brake System.................................................................................................94Left Brake Pedal Actions................................................................................................95Speed Limiter..................................................................................................................97

IMPLEMENT ELECTROHYDRAULIC SYSTEM............................................................98Implement Electronic Control System ...........................................................................99Implement Control Levers............................................................................................106Fine Modulation............................................................................................................109Autodig Control Arrangement ......................................................................................111Implement Hydraulic System - HOLD.........................................................................114Tilt Control Valve - HOLD...........................................................................................116Implement Hydraulic System - DUMP ........................................................................117Pressure Compensator Valve - HOLD..........................................................................118Load Check Operation ..................................................................................................119Pressure Compensator Operation .................................................................................120Implement Hydraulic System - DUMP ........................................................................124Implement Hydraulic System - RAISE ........................................................................126Implement Hydraulic System - FLOAT .......................................................................128Implement Hydraulic System - TILT BACK AND RAISE .........................................130Implement Hydraulic System - RIDE CONTROL AUTO...........................................132Ride Control Valve - AUTO/TRAVEL BELOW 9.7 KM/H (6 MPH) ........................134Ride Control Valve - AUTO/TRAVEL MORE THAN 9.7 KM/H (6 MPH)...............135Implement Pump and Pump Control Valve ..................................................................138Pump Control Valve - ENGINE OFF...........................................................................139Pump Control Valve - LOW PRESSURE STANDBY.................................................141Pump Control Valve - UPSTROKE..............................................................................142Pump Control Valve - CONSTANT FLOW DEMAND ..............................................143Pump Control Valve - MAXIMUM SYSTEM PRESSURE........................................144Pump Control Valve - MAXIMUM SYSTEM PRESSURE WITH ADDED FLOW DEMAND...................145Implement Valve ...........................................................................................................146Margin Relief Valve......................................................................................................147Pressure Reducing Valve - BELOW THE ADJUSTED SETTING .............................148Pressure Reducing Valve - ABOVE THE ADJUSTED SETTING .............................149Load Sensing Pressure Tap...........................................................................................150Signal Duplication Valve ..............................................................................................154Signal Relief Valve - BELOW ADJUSTED PRESSURE SETTING..........................155Signal Relief Valve - ABOVE ADJUSTED PRESSURE SETTING ..........................156Line Relief Valve - BELOW RELIEF SETTING ........................................................157Line Relief Valve- ABOVE RELIEF SETTIN ............................................................159Line Relief Valve - MAKEUP FUNCTION.................................................................160Quick Coupler System..................................................................................................162



HAND METERING UNIT (HMU) STEERING SYSTEM ..............................................165Steering Pump...............................................................................................................169Steering Pump - ENGINE OFF....................................................................................170Steering Pump - LOW PRESSURE STANDBY..........................................................171Steering Pump - UPSTROKE.......................................................................................172Steering Pump - DESTROKE ......................................................................................173Steering Pump - HIGH PRESSURE STALL ...............................................................174Steering Control Valve..................................................................................................175Steering Neutralizer Valves ..........................................................................................176Steering System - HOLD..............................................................................................178Steering System - GRADUAL LEFT TURN...............................................................180Steering System - FULL LEFT TURN WITH STEERING NEUTRALIZED............181Secondary Steering System ..........................................................................................182Secondary Steering System - GRADUAL LEFT TURN.............................................186

COMMAND CONTROL STEERING (CCS) SYSTEM...................................................188Quad Check Valve ........................................................................................................191Steering Pilot Valve ......................................................................................................192Steering Pilot Valve - NO TURN .................................................................................193Steering Pilot Valve - RIGHT TURN...........................................................................194Steering System - HOLD..............................................................................................196Steering System - GRADUAL LEFT TURN...............................................................197

BRAKE AND HYDRAULIC FAN SYSTEM COMPONENTS.......................................199Brake and Hydraulic Fan System - CUT IN AND MINIMUM FAN SPEED ............201Brake and Hydraulic Fan System - MINIMUM FAN SPEED AT CUT OUT ............202Brake and Hydraulic Fan System - MAXIMUM FAN SPEED AT CUT OUT...........204Brake and Hydraulic Fan Pump....................................................................................211Brake and Hydraulic Fan Pump - ENGINE OFF.........................................................212Brake and Hydraulic Fan Pump - LOW PRESSURE STANDBY ..............................213Brake and Hydraulic Fan Pump - UPSTROKE ...........................................................215Brake and Hydraulic Fan Pump - CONSTANT FLOW...............................................216Brake and Hydraulic Fan Pump - DESTROKE ...........................................................217Brake and Hydraulic Fan Pump - HIGH PRESSURE STALL....................................218Accumulator Charge Valve and Hydraulic Fan Solenoid.............................................219Service Brake Valve......................................................................................................221Brake Hydraulic System - PARKING BRAKE DISENGAGED ................................222Brake Hydraulic System - SERVICE BRAKES APPLIED.........................................223Service Brake Valve - NOT ACTIVATED ...................................................................224Service Brake Valve - ACTIVATED ............................................................................225



CATERPILLAR MONITORING SYSTEM ......................................................................229Fuel Level Sender .........................................................................................................230Hydraulic Oil Temperature Sensor ...............................................................................231Service Brake Pressure Switch .....................................................................................232Axle Oil Temperature Sensors......................................................................................233Differential Pressure Switch in the Right Side Service Bay ........................................234Action Alarm.................................................................................................................236Fuel Level Indicator......................................................................................................237Torque Converter Outlet Temperature Sensor..............................................................238Electrical System ..........................................................................................................239Engine Tachometer .......................................................................................................241Axle Oil Cooler System................................................................................................242

CONCLUSION...................................................................................................................247

HYDRAULIC SCHEMATIC COLOR CODE...................................................................248


NOTES


INTRODUCTION

This presentation discusses the component locations and systems operation for the 950H, the962H Wheel Loaders, and IT62H Integrated Toolcarrier. The new C7 engine, the power train,proportional priority, pressure compensated implement hydraulics, and the steering and brakingsystem operation will be covered.

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IT62H INTEGRATED TOOLCARRIER

950H AND 962H II WHEEL LOADERS

The 950H, the 962H Wheel Loaders, and the IT62H Integrated Toolcarrier are medium wheelloaders in the Caterpillar product line. The serial number prefix for the 950H is K5K Aurorabuilt (N1A Gosselies, J5J Sagami, M1G Brazil), the serial number for the 962H Wheel Loaderis K6K Aurora built (N4A Gosselies, J6J Sagami, M3G Brazil) and the IT62H IntegratedToolcarrier prefix M5G is being built in Brazil only. The operating weight for the 950H isapproximately 18,300 Kg (40,300 lbs), the operating weight for the 962H is approximately19,000Kg (41,900 lbs), and the operating weight for the IT962H is approximately 19,400Kg(42,770 lbs).

The color codes used for hydraulic oil throughout this presentation are:

Red - System or high pressure

Red and White Stripes - 1st Reduced pressure

Red and White Hatched - 2nd Reduced pressure

Orange - Pilot pressure

Blue - Blocked oil

Green - Tank or return oil

Yellow - Active component


3Component Location

This illustration shows the basic component locations on the 950H and 962H. The componentlocations on the 950H and 962H are basically the same as in the "G" series II Wheel Loaders.

Power for the 950H, 962H Wheel Loaders ,and IT62 Integrated Toolcarrier is supplied by theC7 ACERT engine. Power flows from the engine to the torque converter, to theElectronic Clutch Pressure Controlled (ECPC) transmission, through the output transfer gear tofront and rear drive shafts. From the drive shafts, power flows to the bevel gears in thedifferentials, and through the axles.

The wheel loader is equipped with a steering pump, a steering valve, and the steering cylinders.Also, the machine is equipped with an electrohydraulic implement control with a variabledisplacement implement piston pump supplying oil to the 3PC hydraulic valve located in theloader frame.

The machine maybe equipped with an optional electric steering pump that is installed inside therear frame. This pump supplies oil to the steering system with a loss of main steering supplyoil.


C7Engine

Transmission

FrontFinal Drive

RearFinal Drive

RearDrive Shaft

TorqueConverter

FrontDrive Shaft

ParkingBrake

HydraulicTank

EngineECM

Radiatorand ATAAC

ImplementControl Valve

TiltCylinder

LiftCylinder

Tilt PositionSensor

LiftPosition Sensor

ImplementControl Levers

Fan Pump

Power Train andImplement ECM

SteeringValve

Implement andSteering Pumps

FanMotor

SteeringCylinder

Air ConditionerCondenser

Hydraulic FanCooler

AccumulatorCharging Valve

Steering ControlValve

WHEEL LOADER COMPONENTS

Electrical Components Hydraulic Components Power Train ComponentsEngine Components

The wheel loader is equipped with an on demand hydraulic fan system and brake system. Thesystems share a common variable displacement piston pump and accumulator charging valve.The charging valve gives priority to the brake system over the hydraulic fan system. The brakesystem includes the front and rear service brakes with a hydraulic release parking brake.


ENGINE

The C7 ACERT engines utilize the A4 Electronic Control Module (ECM) engine control andis equipped with an Air-to-Air Aftercooler (ATAAC) intake air cooling system. The C7 engineis an in-line six-cylinder arrangement with a displacement of 7.2 L. The C7 engine in the 950His rated at 147 kW (197 net horsepower). The C7 engine in the 962H and the IT62H is rated at157 kw (211 net horsepower). The C7 engines are electronically configured to provide constantnet horsepower through the operating ranges. Constant net horsepower automaticallycompensates for any parasitic loads, allowing the operator to maintain a constant level ofproductivity.

C7 ACERT Technology provides an advanced electronic control, a precision fuel delivery,and refined air management.

The Engine ECM utilizes the Advanced Diesel Engine Management (ADEM IV) to control thefuel injector solenoids and to monitor fuel injection. The fuel is delivered through a HydraulicElectric Unit Injection (HEUI) system.

The C7 ACERT is equipped with a wastegate turbocharger which provides higher boost overa wide range, improving engine response and peak torque, as well as outstanding low-endperformance.

The C7 ACERT engines meet US Environmental Protection Agency (EPA) Tier III EmissionRegulations for North America and Stage IIIa European Emission Regulations.

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5Engine Electrical Block Diagram

This block diagram of the engine electrical system shows the components that are mounted onthe engine which provide input signals to and receive output signals from the Engine ElectronicControl Module (ECM).

Based on the input signals, the Engine ECM energizes the injector solenoid valves to controlfuel delivery to the engine, and the cooling fan proportional solenoid valve to adjust pressure tothe cooling fan clutch.

The two machine interface connectors provide electrical connections from the engine to themachine including the Cat Data Link.

Some of the components connected to the Engine ECM through the machine interfaceconnectors are: the throttle pedal position sensor, the ether aid solenoid, and the ground levelshutdown switch.


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Input Components:

Atmospheric pressure sensor - This sensor is an input to the Engine ECM and is used as areference for air filter restriction. Also, the sensor is used to supply information to the EngineECM during operation at high altitude.

Turbo inlet pressure sensor - This sensor is an input to the Engine ECM to supplyinformation about the air restriction before the turbocharger.

Intake manifold temperature sensor - This sensor is an input to the Engine ECM to supplyinformation about the air temperature entering the intake manifold from the ATAAC.

Intake manifold pressure sensor - This sensor is an input to the Engine ECM supplyinginformation about air pressure (boost) in the intake manifold.

Fuel differential pressure switch - This switch relays information to the ECM that the fuelpressure at the output of the filter base is restricted in comparison to the inlet pressure.

Coolant temperature sensor - This sensor is an input to the Engine ECM supplyinginformation on the temperature of the engine coolant. The ECM uses this information fordemand fan solenoid current, high coolant temperature warnings, engine derates for highcoolant temperature, or logged events.

Engine oil pressure sensor - This sensor is an input to the Engine ECM to supplyinginformation on engine oil pressure. The ECM uses this information for low oil pressurewarnings,.engine derates for low oil pressure, or logged events.

Throttle pedal position sensor - This sensor sends a PM signal to the Engine ECM with theamount of movement of the governor pedal. This signal is used to increase or decrease theamount of fuel by the injectors.

Auto reversing fan switch - This switch is an operator input to the Engine ECM. The operatorcan manually enable the reversing solenoid valve and change the direction of oil flow throughthe hydraulic fan motor .

Ground level shutdown switch - This switch is an input to the Engine ECM. This inputdisables fuel injection when the engine is running or at engine start-up.

Primary and secondary speed timing calibration sensor - These speed sensors are passivespeed sensors that provide a signal similar to a sine wave that varies in amplitude andfrequency as speed increases. The permanent timing calibration sensor monitors the speed andposition of the flywheel.

Key switch ON (+B) - The Key On input to the Engine ECM enables the ECM for operationand allows the Engine ECM to be recognized by any ECM on the machine.


Injection activation pressure sensor - This sensor sends the rail oil pressure feedback data tothe Engine ECM.

Output Components:

+5 Volt - Regulated supply voltage for the sensor inputs to the Engine ECM.

Throttle sensor voltage - Voltage supply for the throttle position sensor.

Analog sensor voltage - Analog voltage for the Turbo inlet pressure sensor.

Intake air heater relay - The start aid relay sends current to the air intake heater to warm theair in the intake manifold for starting the engine in cold weather conditions.

Auto reversing fan solenoid valve - This solenoid valve is used in order to reverse the oil flowoil through the hydraulic fan motor..

Demand fan solenoid valve - Proportional solenoid valve that controls the signal pressure tothe brake and fan pump in order to meet the varying cooling requirements of the machine.

Air filter restriction indicator ON - This indicator illuminates in case of a restriction in theinlet air system.

Intake air heater indicator ON - This indicator illuminates when the air heater relay isenergized.

Injection actuation pressure solenoid - This solenoid electronically controls the high pressureHEUI pump output. This solenoid is confined inside the pump control.

Mechanical electronic unit injectors (6) - Injectors supply a governed amount of fuel to thebasic engine.

Ether aid solenoid - This solenoid is energized when the Engine ECM recognizes that theeither the engine coolant temperature or the intake manifold air temperature is below-9 C (16 F).


Speed/Timing Sensors

The primary speed timing sensor (1) and secondary speed timing sensor (2) are located belowthe Hydraulic Electronic Unit Injector (HEUI) and above the hydraulic fan pump (3). Undernormal operation, the primary speed timing sensor (1) determines the No. 1 compression timingprior to the engine starting. If the primary speed timing sensor is lost, a CID 190 MID 08primary engine speed signals abnormal and the secondary sensor will time the engine with anextended starting period and run rough until the Engine ECM determines the proper firing orderusing the secondary speed timing sensor only. If the secondary speed timing sensor is lost, aCID 342 MID 08 secondary engine speed signals abnormal and the primary sensor will time theengine with an extended starting period and run rough until the Engine ECM determines theproper firing order using the secondary speed timing sensor.

In the case that the signal from both engine speed sensors are lost, the engine will not start.During a running condition, the engine will shutdown.

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7Engine Speed/Timing Calibration Port

The speed/timing calibration port (1) is located on the right side of the machine. Remove theplug in order to install the timing probe. The Engine ECM (2) has the ability to calibrate themechanical differences between the Top Center (TC) of the crankshaft and the timing gear onthe camshaft. A magnetic transducer signals the TC of the crankshaft to the ECM when thenotch (not shown) on a counterweight passes by the transducer (not shown). The speed/timingsensor signals the TC of the timing gear to the Engine ECM. Any offset between the TC of thecrankshaft and the TC of the timing gear is stored into the memory of the Engine ECM.

NOTE: For additional information in troubleshooting the engine, refer to the ServiceManual module Troubleshooting "C7 Engines for Caterpillar Built Machines"(RENR9319) "Engine Speed/Timing Sensor - Calibrate.


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8Fuel System

Fuel is drawn from the fuel tank through the primary fuel filter (10-micron) and water separatorthrough the Engine ECM (for cooling purposes) by a gear-type fuel transfer pump. The fueltransfer pump then pushes the fuel through the secondary fuel filter (2-micron). The fuel thenflows to the cylinder head. The fuel enters the cylinder head and flows into the fuel gallery,where it is made available to each of the six HEUI fuel injectors. Any excess fuel not injectedleaves the cylinder head and flows past the fuel pressure regulator returning to the fuel tank.

The fuel pressure regulator is an orifice that is installed at the rear of the cylinder head. Thefuel pressure regulator maintains fuel system pressure between the fuel transfer pump and thefuel pressure regulator.

From the fuel pressure regulator, the excess fuel flow returns to the fuel tank. The ratio of fuelused for combustion and fuel returned to tank is approximately 3:1 (i.e. four times the volumerequired for combustion is supplied to the system for combustion and injector coolingpurposes).


FuelTransfer Pump

PrimaryFuel Filter /

Water SeparatorSecondaryFuel Filter

Electric FuelPriming Pump

Fuel PressureRegulator

Fuel Gallery

Fuel Tank

C7 ENGINEFUEL DELIVERY SYSTEM

(Optional)Fuel Heater

Engine ECM

HEUIPump

InjectionActuationSolenoid

High Pressure Engine Oil Pressured FuelEngine Lubrication Oil Return Pilot Oil

A pressure differential switch is installed in the secondary fuel filter base and will alert theoperator of a fuel filter restriction. The pressure differential switch compares the filter inletpressure to the filter outlet pressure. When the difference in the inlet and outlet pressurescauses the switch to activate, the Engine ECM will signal the Caterpillar Monitoring System towarn the operator the fuel flow is probably restricted.

A fuel pressure sensor is installed in the secondary fuel filter base and will signal the EngineECM of a high fuel pressure. If the fuel pressure exceeds a pressure of 758 kPa (110 psi) theEngine ECM will log a E096 code.

The HEUI pump is a variable displacement piston pump that intensifies engine oil pressure anddirects that oil to the individual injectors. The injection actuation solenoid is also containedinside the HEUI pump. The solenoid is an output directly from the Engine ECM that controlsthe amount of oil actuation pressure for the amount of fuel injection.


Fuel Transfer Pump

The fuel transfer pump (1) is a gear pump that is attached to the Hydraulic Electronic InjectorUnit (HEUI) (2) between the engine and the secondary fuel filter (not shown). The filtergroups are removed for clarity. The fuel transfer pump is also driven by HEUI. Fuel is drawnfrom the fuel tank, the primary fuel filter and water separator (not shown), through the EngineECM, to the hose (5) by the fuel transfer pump. Then, the fuel is directed to the secondary fuelfilters through the hose (4).

In the high pressure system using the HEUI pump, pressurized oil from the engine lube systemis directed to the pump through hose (7). Then, high pressure engine oil is directed throughtube (6) to the injectors.

Also shown is the connection for the injection actuation solenoid that is located at connector (3).

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Power Derate

The illustration above defines the power derate in relation to the rated torque map and thedefault torque map. The power derate is a percentage reduction from the rated power at a givenengine speed toward the default map at the same rpm.

The derated power is what has changed, not the actual power in all situations. The actualpower rating lost during a derate is calculated as:

Power_Output = Rated Power - (Rated Power - Default Power) * Percentage of Derate

For example, if the engine has a maximum rated power of 500 hp and a 100 hp default torquemap with a 50% derate, the engine will have 300 hp output power. If 250 hp was needed, thenthe operator will not notice any change. If however, 400 hp was needed, there would be only300 hp available due to a derate.


50% Derate

100% Derate

Highest Rated Torque Map

Default Torque Map

Pow

er

Engine Speed

POWER DERATE

Derate

The fuel system is equipped with two filters: a primary fuel filter/water separator (4) and asecondary filter (3).

The primary fuel filter is located on the right side of the machine. The primary filter contains awater separator which removes water from the fuel. Water in a high pressure fuel system cancause premature failure of the injector due to corrosion and lack of lubrication. Water shouldbe drained from the water separator daily, using the drain valve that is located at the bottom ofthe filter.

The electric fuel priming pump (5) is integrated into the primary fuel filter base. The primingpump is activated by toggling the fuel priming pump switch (6). The fuel priming pump isused to fill the fuel filters with fuel after they have been replaced.

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The priming pump will purge the air from the entire fuel system. To activate the fuel primingpump, the key start switch must be in the OFF position.

The fuel system is equipped with a secondary high efficiency fuel filter. Also, installed on thebase is a fuel pressure differential switch (1), and a fuel pressure sensor (2).

The fuel differential pressure switch monitors the difference between the outlet fuel pressureand the inlet pressure. When the fuel differential pressure exceeds 103 kPa (15 psi) a Level 1Warning will be initiated. Then, after 4 hours the Engine ECM initiates a Level 2 Warning andan Engine Derate.

The fuel pressure sensor is used to indicate low fuel pressure. With the C7 HEUI engine, lowfuel pressure initiates a low fuel pressure derate of 50%. The Engine ECM limits the rail oilpressure because large fueling values will cause late combustion cycles, which results inexcessive smoke and possible engine damage. Also, at startup and after 10 seconds, with lowfuel pressure a 94-11 event is logged. The reason for this event is to detect situations where thefuel has drained out of the rail and is taking excessive time to reach the required pressure.


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High Fuel Filter Restriction Derates

When the differential pressure switch recognizes a fuel pressure of 103 kPa (15 psi) for 3minutes, the Engine ECM will initiate a Level 1 Warning.

When the differential pressure switch recognizes 15 psi across the filter for 4 hours, the EngineECM will initiate a Level 2 Warning. With the Level 2 Warning initiated a 17.5 % derate isapplied to the engine. After 1 second, the Engine ECM will initiate a second derate of 17.5%.The total derate will be 35%.


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The illustration shows a top view of the engine. The Injection Actuation Pressure (IAP) sensorlocated in the top of the engine block measures the hydraulic actuation pressure and sends theactual oil pressure to the Engine ECM. The ECM compares the desired pressure to the actualpressure in order to figure the proper amount of oil pressure to be sent to the injectors.


Engine Inlet Air System

In the engine inlet air system, the air enters the compressor section of the turbocharger (4)through the air cleaner (2). The compressor directs the air through the ATAAC (3), the airintake manifold, and to the cylinder head.

Exhaust exits the cylinder head to the turbine housing. From the turbine housing, the turbinewheel directs the exhaust out of the Turbo and out through the muffler (1).

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The C7 ACERT engines are equipped with a wastegate turbocharger which provides higherboost over a wide range, improving engine response and peak torque, as well as outstandinglow end performance. All of the exhaust gases go from the exhaust manifold through theturbocharger.

The exhaust gases enter the turbocharger and drive the turbine wheel. The exhaust exits theturbocharger through turbine wheel outlet (2) to the muffler. The turbine wheel is connected bya shaft to the compressor wheel. The turbine wheel rotates the compressor wheel at very highspeeds. The rotation of the compressor wheel pulls clean air through the compressor housingair inlet (1). The compressor wheel blades force air into the cylinder head to the inlet valves.The increased amount of forced air enables the engine to burn more fuel, producing increasedpower. The engine can operate under low boost conditions. During a lower boost condition,the canister closes the wastegate, allowing the turbocharger to operate at maximumperformance. Under high boost conditions, the wastegate opens. The open wastegate allowsexhaust gases to bypass the turbine side of the turbocharger. The rpm of the turbocharger islimited by bypassing a portion of the exhaust gases around the turbine wheel of theturbocharger.

NOTE: The wastegate calibration is preset at the factory.


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Turbo Inlet Pressure Sensor

The turbocharger inlet pressure sensor (1) is located in the tube that is between the air filtergroup (2) and the inlet to the compressor housing of the turbocharger.

The turbocharger inlet pressure sensor measures restriction of air flow through the air filtergroup and the inlet to the turbocharger. Restriction of the air flow to the turbocharger willinitiate a warning and engine derate.


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Air Inlet Restriction Derate

The turbo inlet pressure sensor measures the restriction of the air inlet that is flowing to theinlet of the compressor housing of the turbocharger. When the pressure difference between theTurbo inlet pressure sensor and the atmospheric sensor read a difference of 9.0 kPa, theEngine ECM will derate the engine approximately 2%. The Engine ECM will then derate theengine 2% more for every 1 kPa difference up to 10%.

Typically the atmospheric (barometric) pressure sensor is 100 kPa at sea level. As the airrestriction increases, the difference will increase. The first derate will occur when thedifference is approximately (100 kpa minus 91 kPa.= 9 kPa). If the air inlet restriction is 92.5kPa (a pressure that is between 7.5 kPa and 9 kPa) for 10 seconds, the Engine ECM will initiatea Level 1 Warning.

If the air restriction goes to the point that the turbo inlet pressure sensor sees a difference of91.0 kPa (a pressure that is 9.0 KPa) for 10 seconds, then the Level 2 Warning will occur, andthe engine will derate.

NOTE: This air inlet restriction derate is a latching derate. The derate will remainactive until the machine is shut down.


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Engine Oil Pressure Sensor

The engine oil pressure sensor (1) is located on the left side of the engine and the right side ofthe machine near the Engine ECM (2). The sensor monitors the pressure of the engine oil.

The engine oil pressure sensor is one of the many sensors that require a regulated 5.0 VDC forthe sensor supply voltage. The sensor outputs a variable DC voltage signal.

The Engine ECM will use the information supplied oil pressure sensor to output warning levelsto the Caterpillar Monitoring System and engine derates.


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Low Oil Pressure Derate

This illustration shows a graph with the two different warning levels for low oil pressure.

When the oil pressure is below (154 kPag @ 1600 rpm) the blue line, the cat monitoring systemwill enable the low oil pressure Level 1 Warning. Change machine operation or performmaintenance to the system.

When the oil pressure is below (104 kPag @ 1600 rpm) the red line, the cat monitoring systemwill enable the low oil pressure Level 3 Warning. The operator should immediately perform asafe engine shutdown.

Also, with the Level 3 Warning, the Engine ECM initiates a 35% engine derate.

If the signal between the Engine ECM and the oil pressure sensor is lost or disabled, the EngineECM will initiate a low engine oil pressure Level 1 Warning.


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Coolant Temperature Sensor

The coolant temperature sensor (1) is installed on the engine block behind the primary fuelfilter and water separator. The primary fuel filter and water separator is transparent to show thelocation of the component. The coolant temperature sensor monitors the temperature of thefluid in the coolant system. The coolant sensor information sent to the Engine ECM is used forWarning Levels that are sent to the Caterpillar Monitoring System and engine derates.


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23

High Coolant Temperature Derate

The coolant temperature sensor measures the temperature of the coolant.

When the temperature of the coolant exceeds 108 C (226 F), the Engine ECM will initiate aLevel 1 Warning.

When the temperature of the coolant exceeds 111 C (231 F), the Engine ECM will initiate aLevel 2 Warning. At 111 C (231 F) the Engine ECM will initiate a 25% derate. Refer to theillustration above for the remainder of the high engine coolant temperature derates. At 100%derate, the engine available power will be approximately 50%.


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Intake Manifold Sensors

The upper illustration shows the intake manifold temperature sensor (1).

The intake manifold temperature sensor (1) is used to monitor the air temperature flowing intothe intake manifold. The intake manifold pressure sensor (3) is used to monitor the air pressurein the intake manifold. The Engine ECM (5) also uses the temperature sensor as one of the keytarget temperatures to control the fan speed in the hydraulic fan system and as an input to theEngine ECM for the virtual exhaust temperature derate. Also shown is the primary fuel filterand water separator (4).

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The atmospheric pressure sensor (2) is located on the right side of the machine on the engine.The Engine ECM uses the sensor as a reference for air filter restriction, and derating the engineunder certain parameters. All pressure sensors in the system measure absolute pressure and,therefore, require the atmospheric (barometric) pressure sensor to calculate gauge pressures.

The atmospheric pressure sensor is one of the many sensors that require a regulated 5.0 VDCfor the sensor supply voltage. The atmospheric pressure sensor outputs a variable DC voltagesignal.


26

Intake Manifold Air Temperature Sensor Derate

The intake manifold air temperature sensor measures the temperature of the air that is flowingto the intake manifold. The sensor is used to initiate warning levels in the CaterpillarMonitoring System and engine derates for the C7 ACERT Engine.

After the engine is running for at least 3 minutes and if the intake manifold air temperature goesabove 90 C (194 F), the Engine ECM will initiate a Level 1 Warning.

After the engine is running for at least 3 minutes and if the intake manifold air temperature goesabove 110 C (230 F), the Engine ECM will initiate a Level 2 Warning. With the Level 2Warning, the Engine ECM signals the engine to initiate a 3% derate. This derate will have a20% upper limit.


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Virtual Exhaust Temperature Derate

An engine derate can occur due to a estimated (virtual) high exhaust gas temperature. TheEngine ECM monitors barometric pressure, intake manifold temperature, and engine speed toestimate exhaust gas temperature. Certain conditions (high altitude, high ambient temperatures,high load and full accelerator pedal throttle, barometric pressure, intake manifold temperature,and engine speed) are monitored to determine if the engine derate should be enabled. TheEngine ECM determines a maximum fuel delivery percentage to maintain safe maximum poweroutput under load. This calculation is new to the off-road Tier III engines and is used in placeof the previous altitude compensation derate strategy.

This event is to inform the mechanic that a derate has occurred because of operating conditions.Generally, this is normal and requires no service action.

The Engine ECM will process all derate inputs in the highest derate priority selector. The mostcritical derate condition input will be used to adjust fuel system delivery limiting engine powerto a safe level for the conditions in which the product is being operated, there by preventingelevated exhaust temperatures.


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The virtual exhaust temperature derate will log a 194 event code. The derate will enable aLevel 1 Warning and eventually a Level 2 Warning. The level of the warning will depend onthe conditions that are sent to the Engine ECM.

The following conditions must be met in order to initiate a virtual exhaust temperature derate.

- No CID 168 01 FMI (low battery voltage to the Engine ECM) are active.

- No active intake manifold pressure sensor faults.

- No active atmospheric pressure (barometric) sensor faults.

- No +5 V sensor voltage codes active.

- The virtual exhaust temperature derate must be the highest derate.

- More fuel is being requested than the virtual exhaust temperature derate will allow.

This derate is triggered by the information inferred by the Engine ECM, rather than anindividual sensor as with the previous single derate strategies. If you think this derate ispossibly being imposed incorrectly check for event codes on the high intake manifoldtemperature and correct those first. Also, make sure the aftercooler is unobstructed. Foradditional information about troubleshooting, refer to the troubleshooting manual for theparticular engine that is being serviced.


The intake manifold air heater (1) is located in the intake manifold and the relay (2) is locatedon a bracket behind the fuel filter and water separator. The Engine ECM receives temperaturedata from both the intake manifold air temperature and coolant temperature sensors to controlenergizing of the heater relay. If the altitude is above 1675 m (5500 ft) use the high altitudecoolant and intake manifold air temperature. The high altitude heater control temperatures is53.3 C (127 F).

The intake manifold air heater has the following five cycles.

1. The first cycle is the power-up. The heater and the indicator lamp are energized for twoseconds at power-up regardless of the temperature.

2. The second cycle is the pre-heat. The heater and indicator lamp will be energized to 30seconds if the coolant and/or air temperatures are below 25 C (77 F). After 30 seconds,the heater and indicator lamp are turned OFF if the engine speed is at 0 rpm.

3. The third is the crank cycle. The heater and indicator lamp will be ON continuously ifthe coolant and/or air temperature is below 25 C (77 F) as long as the engine is beingcranked.

4. The forth is the engine running cycle. Once the engine is at low idle and the coolantand/or air temperature is below 25 C (77 F), the heater and indicator lamp areenergized to an additional 7 minutes.

5. The fifth is the post-heat cycle. If the coolant and/or air temperatures are below 25 C(77 F) the heater and lamp are cycled ON and OFF for an additional 13 minutes. Thecycle is ten seconds ON and then 10 seconds OFF.

Also shown is the Injection Actuation Pressure (IAP) sensor (3).

28


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The left side of the front dash panel shows the AIR FILTER RESTRICTED condition. Theilluminated indicator is enabled by an output from the Engine ECM through the Cat MonitoringSystem.

The right side of the front dash panel shows the intake air heater ON condition. Theilluminated indicator is also enabled by an output from the Engine ECM through the CatMonitoring System.


LEFT SIDE PANEL RIGHT SIDE PANEL

The ether aid system is an attachment on the 950H, the 962H Wheel Loaders, and the IT62HIntegrated Toolcarrier. This attachment may be added for engine starts in cooler ambienttemperatures. The ether aid system consists of the following components:

- Ether aid bottle (1)

- Ether aid solenoid (2)

- Ether aid connector installed on the intake manifold (3)

30

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When the machine is operated in a cold ambient environment, ether may be installed alongwith the intake manifold air heater to start the engine. In order to use the ether aid, the etheraid system must be installed in the engine compartment and the ether aid must be enabledthrough Caterpillar Electronic Technician (ET).

For the engines in the 950H, 962H wheel loaders, and the IT62H Integrated Toolcarrier, thecold start strategy is dependent on whether the intake manifold air temperature or the enginecoolant temperature registers as the lower temperature. The Engine ECM looks at the lowesttemperature between the two sensors and that information registers into the temperature map.The ECM compares the temperature map against the atmospheric pressure sensor and decideswhether ether is required to start the engine.

If either temperature is below -9 C (15 F) continuous metered ether injection is sent to theintake manifold at connector (3). If the temperature is above -9 C (15 F), the intake manifoldair heater is enabled.


32

Engine Idle Management System (EIMS)

Engine Idle Management System (EIMS) sets the engine idle to maximize fuel efficiency.Also, this system uses new and improved software to benefit the customer with reduced soundlevels, reduced emissions, machine ability to set machine parameters to the working conditions,machine ability to set machine to working applications, and increased battery durability.

Work Mode - This mode allows the working idle to be programmed according to the customer'sapplications requirements. The work mode idle can be adjusted to a higher or lower rpmthrough Caterpillar Electronic Technician (ET). The engine idle range is between 650 rpm and1000 rpm. In order to go into the work mode, the percentage of fan bypass must be less than23%.

Warm up Mode - In a cold weather operation, the default engine rpm will be set to 1100 rpm inorder to generate additional engine heat, keeping the engine warmer. This mode monitors thecoolant temperature and intake manifold temperature. When the coolant temperature is below80 C (176 F) or the intake manifold temperature is below 15 (60 F) and the warm mode isenabled, the machine will time out for 10 minutes. After ten minutes, the coolant temperatureis below 70 C (158 F) and the machine has been in the warm up mode, the engine will be inwarm up mode. If the machine has not been in warm up mode but the intake manifoldtemperature is less than 5 C (41 F), the engine will go into the warm up mode.


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Also, the transmission speed selector must be in the NEUTRAL position, the parking brakeengaged, and the throttle position sensor output less than 5% for the engine to go to the warmup mode idle.

Hibernate Mode - This mode is initiated only when the transmission speed selector switch is inthe NEUTRAL position, the parking brake is engaged, the throttle position sensor output is lessthan 5%, the coolant temperature is above the EIMS default, the fan bypass is above 23%, andthe implement control levers are not activated. When these parameters are met along with a 10second period after the parking brake is engaged, the hibernate mode will lower the engine idleto 600 rpm. The engine will idle at 600 rpm until one of the above parameters are no longermet.

Low Voltage Mode - In this mode, the engine idle will ramp up to 1100 rpm when the batteryvoltage drops below 24.5 VDC and he engine has been running for 5 minutes. The low voltagemode feature is standard on all machines with EIMS with high current drain due to heavyelectrical loads from custom attachments. When the battery voltage is greater than 24.5 VDC,the engine idle will return to the current working low idle speed. The 24.5 battery voltage is adefault and can not be reconfigured in ET.


33

POWER TRAIN

This illustration shows the major components in the power train.

Power from the engine flows to a 360 mm (14.5 inch) diameter torque converter. The torqueconverter output shaft is splined to the input shaft of the electronically controlled power shifttransmission.

The transmission output shaft is splined to the output transfer gear. The output transfer geartransmits power from the transmission to the front and rear drive shafts.

Power from the transmission output shaft flows through the front drive shaft and the parkingbrake to the front pinion, bevel gear, differential and axles to the final drives.

Power from the transmission output shaft also flows through the rear universal joint group tothe rear pinion, bevel gear, differential and axles to the final drives.

Power train movements and operations are controlled through the Power Train ECM.


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Power Train Electrical System

This illustration shows the input components which provide power or signals to the PowerTrain ECM.

Power Train ECM Inputs:

Shift lever upshift, downshift, forward, neutral, reverse: Combines control of thetransmission shifting to a single input device. The shift lever can be pushed forward, backward,or placed in the middle position for machine direction. The lever is rotated in order to changethe speeds of the transmission. This is the standard control for shifting that comes with theHand Metering Unit (HMU) steering.

Direction switch forward, neutral, reverse, upshift, and downshift: Combines control of thetransmission shifting with a single input device. The 3 position rocker switch controls directionand the 2 thumb switches control upshift and downshift. This is the control for shifting thatcomes with the Command Control Steering (CCS).

Key start switch: Provides a signal to the Power Train ECM when the operator wants to startthe engine. The direction switch/shift lever must be in the NEUTRAL position before thePower Train ECM will permit engine starting.


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Variable shift control selector switch: The variable shift control switch is an input of thePower Train ECM. The switch allows the selection of a range of shifting points in the PowerTrain ECM for each speed. The switch has three inputs to the Power Train ECM.

Transmission output speed sensors 1 and 2: These sensors measure the transmission outputspeed in the range of 25 to 3000 rpm. By looking at the difference in phase in between these 2sensors, direction can be derived.

Torque converter output speed sensor: Measures the torque converter speed in the range of25 to 3000 rpm.

Auto/manual speed selector switch (HMU): Signals the Power Train ECM which shift modethe operator wants to operate on a standard machine. The operator can select between manualshifting or automatic shifting in the range of gears 4 to 2 or in the range of gears 4 to 1.Maximum gear, if lower gear than 4 is desired, will be determined by the shift lever position.

Auto/manual Speed selector switch (CCS option): Signals the Power Train ECM which shiftmode the operator wants to operate on a machine with the optional Command Control Steering.The operator can select between manual shifting and automatic shifting with maximum gear of4, 3 or 2 and also a 4 to 1 range shifting mode.

Primary steering pressure switch: Sends a signals the Power Train ECM if the steeringsystem loses steering pressure.

Secondary steering pressure switch: The switch informs the Power Train ECM that thesecondary steering pump is correctly building up pressure. The switch is used as feedback forthe startup test and the manual switch test to ensure that the Secondary steering system isoperating properly.

Left brake pedal position sensor: Signals the position of the torque converter pedal to thePower Train ECM. The position of the pedal is being used to downshift the transmission andneutralize the transmission during operation. Both the downshifting and neutralization functionof the pedal can be disabled and hence the pedal would function as a brake pedal only

Parking brake pressure switch: Provides a signal to the Power Train ECM when the pressureis adequate to release the parking brake.

Ride control switch (OFF, SERVICE, AUTO): Signals the Power Train ECM which modethe operator wants to operate. The operator should never operate in SERVICE mode. Thismode is for service only.

Secondary steering test switch: Provides an input to the Power Train ECM that will enablethe secondary steering pump.

Transmission neutralizer disable switch: Provides an input to the Power Train ECM that willdisable the the left pedal neutralization of the transmission.


Heated mirror switch: Provides an input to the Power Train ECM that will enable the heatedmirror attachment (if equipped).

Transmission oil temperature sensor: Provides an input to the Power Train ECM with thetemperature of the transmission oil.

Implement pod downshift switch: The downshift switch provides an input to the Power TrainECM to downshift the transmission. This switch is only used on a HMU steering machine.

Engine speed: The Power Train ECM receives the engine speed over the CAN Data Linkfrom the Engine ECM.

Location code enable (grounded): The location code enable is a grounded input signal to thePower Train ECM that enables the location code detection feature to become active. J1-32 pinon the Power Train ECM connector is connected.

Location code 2 (grounded) : The location code pin number 2 is a grounded input signal thatestablishes the ECM is dedicated to the Power Train operation. J1-27 pin on the Power TrainECM connector is connected.

+24 battery voltage: Unswitched power supplied to the Power Train ECM from the battery.


The Power Train Electronic Control Module (ECM) (arrow) is the central component in theelectronic control system. The ECM is located at the right rear of the cab. The rear panel mustbe removed for access to the ECM. The Power Train ECM will be located behind theoperators seat and have the connectors horizontal to each other.

The ECM makes decisions based on switch-type and sensor input signals and memoryinformation. Input signals to the ECM come from the operator's station, the machine, and thetransmission.

The operator's station input components consist of direction and shift switches, the neutralizerand neutralizer override switches, the park brake switch, the key start switch, and theauto/manual select switch. Optional switch inputs are the ride control switch and the secondarysteer test switch.

The machine input components are the engine speed sensor, the primary steering pressureswitch, the optional secondary steering pressure switch, and the Caterpillar Monitoring Systemmessage center module.

The transmission input components are the transmission oil temperature sensor, the torqueconverter output speed sensor, and the two transmission output speed sensors.

The ECM communicates with other electronic control modules, such as the CaterpillarMonitoring System, the Engine Electronic Control Module (ECM), and the ElectrohydraulicElectronic Control Module (ECM), through the Cat Data Link. The Cat Data Link allows thetransmission ECM to receive and send information.

35


The power train and the implement use the same A4M1 Electronic Control Module (ECM). Toenable the A4M1 Electronic Control Module ECM for power train functions, contact (J1-27) isgrounded. Contact (J1-32) is grounded in order to enable the ECM.

The Power Train ECM responds to machine control decisions by sending a signal to theappropriate circuit which initiates an action. For example, the operator selects an upshift withthe shift lever. The Power Train ECM interprets the input signals from the shift lever, evaluatesthe current machine operating status, and energizes the appropriate modulating valve.

The Power Train ECM receives three different types of input signals:

1. Switch input: Provides the signal line to battery, ground, or open.

2. PM input: Provides the signal line with a square wave of a specific frequency and avarying positive duty cycle.

3. Speed signal: Provides the signal line with either a repeating, fixed voltage level patternsignal or a sine wave of varying level and frequency.

The Power Train ECM has three types of output drivers:

1. ON/OFF driver: Provides the output device with a signal level of +Battery voltage(ON) or less than one Volt (OFF).

2. PM solenoid driver: Provides the output device with a square wave of fixed frequencyand a varying positive duty cycle.

3. Controlled current output driver: The ECM will energize the solenoid with 1.25 ampsfor approximately one half second and then decrease the level to 0.8 amps for theduration of the on time. The initial higher amperage gives the actuator rapid responseand the decreased level is sufficient to hold the solenoid in the correct position. Anadded benefit is an increase in the life of the solenoid.

The Power Train ECM controls the transmission speed and directional clutches. The PowerTrain ECM interprets signals from the shift lever to signal the transmission to perform thefollowing options: Upshift, Downshift, Forward, Neutral, and Reverse.

The Power Train ECM communicates through the CAT Data Link. The CAT Data Link allowshigh speed proprietary serial communications over a twisted pair of wires. The CAT Data Linkallows different systems on the machine to communicate with each other and also with servicetools such as Caterpillar Electronic Technician (ETC).

The Power Train ECM has built-in diagnostic capabilities. As the Power Train ECM detectsfault conditions in the power train system, it logs the faults in memory and displays themthrough the Caterpillar Monitoring System.


Engine Start Switch and Diagnostic Service Tool Connector

The engine key start switch (1) signals the Power Train ECM that the operator wants to start theengine. The ECM determines if the transmission directional switch (not shown) is in theNEUTRAL position. When the directional switch is in the NEUTRAL position and the keystart switch (1) is turned to the START position, the ECM energizes the starter relay.

The diagnostic service tool connector (2) for a laptop computer using Caterpillar ElectronicTechnician (ETC) is on the front panel on the right side.

A laptop computer with ETC can be used for calibrating, checking and clearing fault codes, andmonitoring system inputs and outputs for troubleshooting the transmission system.

Also shown are the the hazard switch (3), and the 12 Volt adapter socket (4).

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Transmission Shift Lever

This is an illustration of the standard type of transmission shift lever control group that is foundon the 950H/962H Wheel Loaders. This control group is found on machines with conventional(HMU) steering systems.

The shift lever is mounted on the left side of the steering column (arrow). The operator movesthe shift lever forward to travel in the FORWARD direction or toward the rear to travel in theREVERSE direction.

FIRST through FOURTH speeds are selected by rotating the shift lever.

When the transmission is in the Manual mode, the transmission ECM allows the shift lever tocontrol the transmission. The transmission ECM shifts the transmission to the exact gear anddirection shown on the shift lever.

When the transmission is in the Automatic mode, the shift lever selection is the maximum gearthe transmission will obtain. The transmission ECM will automatically select the correct speedclutches (SECOND, THIRD, or FOURTH) based on the engine and transmission output speeds.

37


Transmission Shift Control

This illustration shows the transmission shift control for the optional Command ControlSteering (CCS).

The directional control switch (1), and the upshift/downshift switches (2) are mounted on theleft side of the half moon shaped steering wheel.

The directional control switch is a three-position rocker switch which the operator selects eitherFORWARD (toggle forward), NEUTRAL (center position), or REVERSE (toggle backward)directions. The switch position the operator selects will CLOSE (grounds) that particularcontact while the remaining two contacts are OPEN. Closing a switch contact sends a signal tothe Power Train ECM indicating the direction that is being selected by the operator.

The upshift switch/downshift switches are identical in construction and operation. When theoperator wants to manually shift to a higher or lower gear, the upshift switch or downshiftswitch is pressed. Each switch has two input connections at the Power Train ECM. When theswitches are not activated, one connection is closed (grounded) and the other connection isopen. When the operator pushes the upshift or downshift switch, the selected switchmomentarily reverses connections to signal the Power Train ECM to change to the desiredspeed.

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2

This illustration shows the location of the ride control ON/OFF/AUTO switch (1). The ridecontrol switch has three positions. In the center position, ride control is disabled. In the UPposition (as shown) the ride control switch is in the AUTO position. With the switch in AUTO,the ride control system will be enabled when the machine is traveling at least 9.5 km/h (6.0mph). The SERVICE position (as shown on the switch) is used for service to the ride controlsystem.

The transmission neutralization disable switch (2) is used to disable the neutralization of the leftbrake pedal. Pressing the upper section of the switch will activate the override. When theneutralization is enabled, the left brake pedal will not neutralize the transmission, but willfunction as a service brake only. The normal, default position of the switch is the lower(released) position

The heated mirror switch (3) enables the heated mirror relay that is located behind theoperator's seat below the Power Train ECM.

If the machine is equipped with the optional secondary steering, there will be a secondarysteering test switch (4) mounted in the blocked position on the panel. When the switch isdepressed it feeds a ground signal to a relay and also to a switch input on the Power TrainECM. The relay turns on the secondary steering pump motor, which builds up pressure in thesteering hydraulic lines.

The Power Train ECM is monitoring the pressure of the secondary steering hydraulic lines toensure the pressure has increased to an acceptable level while the pump is running.

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If the switch is depressed and the pressure is not increased to the acceptable level within 3seconds, the secondary steering warning indicator will be illuminated to indicate that the pumpis not functioning properly.


The 950H and 962H Wheel Loaders and IT62H Integrated Toolcarrier are equipped with avariable shift control switch (1). The Power Train (ECM) uses the position of the variable shiftcontrol switch and the engine speed in order to determine the autoshift points for thetransmission. The variable shift control switch has three inputs to the power train electroniccontrol module (ECM).

The auto/manual gear selector switch (2) sends a signal to the Power Train ECM to controlshifting mode in auto. The Power Train (ECM) shifts the transmission automatically. ThePower Train ECM evaluates the input that is sent from the engine speed sensor, thetransmission speed sensors, the torque converter output speed sensor, and the left brake pedalposition sensor in order to regulate transmission shifts. The automatic mode of operation isrepresented by two numbers that are separated by a dash. The first number indicates the speedof the transmission when the transmission is placed into gear. The second number indicates thehighest speed of the transmission when the machine is travelling.

For example, place the autoshift control switch into the 2-4 position. The machine willautomatically shift into second gear when the transmission is placed into gear. Thetransmission will automatically upshift into fourth gear as the machine accelerates.

The Power Train ECM does not allow upshifts to a speed that is higher than the speed that isselected with the transmission direction and speed control lever. An automatic downshift fromsecond speed to first speed occurs only if the autoshift switch is in the 1-4 position.

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This illustration shows the panel with the optional Command Control Steering. TheAuto/Manual gear selector switch (arrow) sends a signal to the Power Train ECM to controlshifting mode in auto. In the MANUAL position, the operator is responsible for upshifting anddownshifting the transmission. The Power Train ECM automatically shifts the transmission ifthe autoshift switch is in one of the four AUTO positions and the left brake pedal must bereleased. The Power Train ECM evaluates the inputs that is sent from the engine speed sensor,transmission speed sensors, the torque converter output speed sensor, and the left brake pedalposition sensor in order to regulate transmission shifts.

When the machine is operating in "AUTO" mode, the transmission speed selector switch can beused in order to downshift the transmission. This switch is normally used to downshift fromsecond speed to first speed in order to load a bucket. The transmission will remain in thedownshifted gear for three seconds after the switch is released. Then, automatic shifting willresume. If the transmission is downshifted to first speed, the machine remains there until thereis a direction change or a manual upshift.

For example, place the autoshift switch into position "3." The machine will automatically shiftinto second gear when the transmission is placed into gear. The transmission will automaticallyupshift into third speed when the machine accelerates. An automatic downshift from secondspeed to first speed occurs only if the autoshift switch is in the 1-4 position.

The Power Train ECM does not allow automatic upshifts to a speed that is higher than thespeed that is selected with the auto/manual switch. The autoshift switch is used to select thetop speed for the transmission when the transmission is in the AUTO mode. There are fourmodes of automatic operation: 4 position, 3 position, 2 position, and 1-4 position.

41


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The Power Train ECM receives inputs from three speed sensors on the transmission. The threespeed sensors are:

- the No. 1 output speed sensor (1)

- the No. 2 output speed sensor (2)

- the torque converter output speed sensor (3)

The output speed sensors (1 and 2) are positioned out of phase with each other. The PowerTrain ECM uses the phasing of the input data to determine the direction of rotation of theintermediate and output gears. The torque converter output speed sensor measures torqueconverter output speed in the range of 25 to 3000 rpm. The speed sensor information is alsoused by the Power Train ECM to set and adjust transmission shift points.


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The Power Train ECM has no direct feed back information to determine if clutch engagementand disengagement is completed. The Power Train ECM uses the speed sensor information,including the engine speed sensor data, to measure expected clutch slippage and planetaryspeeds to ensure the transmission is shifting according to the application program stored in theECM memory.

The torque converter speed sensor (3) sends the torque converter speed to the Power TrainECM.

A passive (two-wire) magnetic frequency-type sensor converts mechanical motion to an ACvoltage. A typical magnetic pickup consists of a coil, a pole piece, a magnet, and a housing.The sensor produces a magnetic field that, when altered by the passage of a gear tooth,generates an AC voltage in the coil. The AC voltage is proportional to speed. The frequencyof the AC signal is exactly proportional to speed (rpm).

Magnetic pickup sensors rely on the distance between the end of the pickup and the passinggear teeth to operate properly. Typically when the pickup is installed, it is turned in until thesensor makes contact with the top of a gear tooth and then turned back out a partial turn beforeit is locked in place with a locking nut. A weak signal may indicate the sensor is too far awayfrom the gear. It is important to check the specifications when installing these sensors to insurethe proper spacing.

Transmission speed sensors may be used in pairs. The sensors are often called upper andlower, top and bottom, or primary and secondary referring to the operating range they aredesigned for. Although the sensors have an optimum operating range, in case of a failure theECM will use the signal from the remaining sensor as a backup. The speed sensor may bechecked for both static and dynamic operation. With the sensor disconnected from the machineelectrical harness, a resistance reading of the pickup coil (measured between pins) should reada coil resistance of approximately 1075 ohms. Some magnetic pickups may measure as high as1200 ohms. The resistance value differs between pickup types, but an infinite resistancemeasurement would indicate an open coil, while a zero reading would indicate a shorted coil.


Transmission Oil Temperature Sensor

The transmission oil temperature sensor (1) is a two-wire passive temperature sensor that islocated on the right side of the machine. The sensor is an input to the Power Train ECM. Theoil temperature sensor information is used to adjust transmission clutch fill times.

The transmission oil temperature sensor information is also sent by the Power Train ECM to theCaterpillar Monitoring System over the Cat Data Link.

Also shown are the torque converter oil temperature sensor (2) and the implement pump (3).

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Left Brake Pedal Position Sensor

The left brake pedal position sensor (arrow) is located in the cab as part of the left brake pedal.

The position sensor (left brake pedal) sends an input to the Power Train ECM. The sensorcontinuously generates a 500 Hz PM signal. The duty cycle varies in proportion to the positionof the left brake pedal position sensor. The left pedal position sends a change in the inputsignal to the Power Train ECM. The ECM measures the duty cycle in order to determine theposition of the pedal for downshifting the transmission and neutralizing the clutches.

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Implement Pod Downshift Switch And Remote FNR Switch

The downshift switch (1) is located on the implement pod. If the machine is equipped with ajoystick, the downshift switch will be located on the joystick handle.

When the Power Train ECM is operating in the Manual Mode, depressing the downshift switchwill cause a downshift from SECOND speed to FIRST speed. In the Manual Mode, thedownshift switch will not shift from FOURTH to THIRD speed or from THIRD to SECONDspeed. The transmission will remain in FIRST speed until one of the following conditionsoccurs:

1. A directional shift is made.

2. The shift lever is moved to NEUTRAL before selecting a speed.

3. The shift lever is turned to FIRST speed and then to another speed.

When operating in the Automatic mode, depressing the downshift switch causes thetransmission ECM to downshift the transmission at a higher than normal ground speed.Pressing and immediately releasing the downshift switch causes the transmission ECM toimmediately downshift the transmission one speed range. A downshift will occur only if themachine speed and engine speed will not result in an engine overspeed.

Automatic shifting is disabled for five seconds after the downshift switch is pressed. After fiveseconds, automatic shifting, based on speed sensor inputs, is reactivated.

NOTE: The remote FNR switch (2) is only installed on the machines that are equippedwith the standard HMU steering.

45


1 2

Parking Brake Pressure Switch

The parking brake pressure switch (1) is a normally closed switch with the parking brakeengaged. When the parking brake is engaged, the parking brake indicator light (3) will beilluminated. When the parking brake knob is pushed to the IN position, the parking brakevalve (2) will direct oil pressure to the parking brake release cylinder. The switch state willchange, the parking brake indicator light will not be illuminated, and the Power Train ECM willreceive a signal that the parking brake is dis-engaged.

The parking brake pressure switch is located on the right side of the machine above the servicebay. The cover is transparent to show the location of the parking brake pressure switch.

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Based on the input signals, the Power Train ECM energizes the appropriate transmission controlmodulating valve for speed and directional clutch engagement. The Power Train ECM alsoenergizes the starter relay when starting the machine and the back-up alarm when the operatorselects a reverse gear.

The Cat Data Link connects the Power Train ECM to the other machine ECMs. The data linkalso connects the ECM to the Caterpillar Monitoring System and electronic service tools suchas Caterpillar Electronic Technician (ETC).

Power Train ECM Outputs:

Engine start relay: The Power Train ECM energizes the key start relay when the appropriateconditions are met to start the engine. Controls the current between the key start switch and thestarter relay.

Transmission oil filter bypass indicator LED: The Power Train ECM illuminates theindicator LED when the oil is bypassing the transmission filter.

Low fuel level warning indicator LED: The Power Train ECM illuminates the indicator LEDwhen the fuel level in the tank is below 10% of total fuel tank volume as read by the fuel levelsensor (input to EMS-III communicated over Cat Datalink).


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Ride Control ON indicator LED: The Power Train ECM illuminates the indicator LED whenride control is active. Either in AUTO mode when driving above the threshold speed or whenin ON mode.

Clutch solenoids: The solenoids control the oil flow through the respective speed anddirectional modulating valves.

Secondary steering intermediate relay: The Power Train ECM energizes the relay when theloss of steering pressure is detected by the Power Train ECM. The ECM energizes the relayand power is supplied to the secondary steering pump.

Back-up alarm: The Power Train ECM energizes the back-up alarm when the operator selectsthe REVERSE direction. The backup alarm is located on the rear bumper.

Heated mirror relay: The Power Train ECM energizes the relay to send current to the coil towarm the mirror.

CAN-J1939 signal between machine ECMs: Signals sent between the Machine ECMs andproduct Link on the faster CAN Data Link.

Ride Control Solenoid valve 1 (RE): The Power Train ECM energizes the solenoid valve thatcontrols the opening of the antidrift valve allowing flow between the rod end of the liftcylinders and tank.

Ride Control Solenoid valve 3 (HE): The Power Train ECM energizes the solenoid valve thatcontrols the opening of the antidrift valve allowing flow between the accumulator and the headend of the lift cylinders.

Ride Control Solenoid valve 2 (Balance): At engine start-up, the Power Train ECM energizesthe solenoid valve 2. When the Power Train ECM recognizes the ground speed in AUTOreaches the default threshold speed value in the Power Train ECM, the ECM de-energizes thesolenoid 2 for a default time designated through Caterpillar ETC configuration. The pressurebetween the head end of the lift cylinders and the accumulator is balanced. Then the PowerTrain ECM energizes the solenoid 1 and 3 ride control solenoids.

+8 Volts: Regulated power supply providing 8 VDC that is used in order to power the digitalsensors.

Axle Oil Cooler Relay (option): Energized by the Power Train ECM when the axle oiltemperature reaches 65 C (149 F). When the relay is energized, current is sent to theelectromagnetic clutch on the axle oil cooler pump.


Back-up Alarm

The backup alarm (arrow) is located on the right hand side of the machine inside the accessdoor. The alarm sounds when the transmission directional lever (HMU) or the transmissiondirectional switch (CCS) is placed in the REVERSE position.

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Warning Panel - Left Side

The illustration shows the warning panel on the left side of the dash panel. These indicators aredriven outputs of the Power Train ECM.

The transmission oil filter bypass (1) is located on the top right hand side. This alarm isilluminated when the transmission oil filter is bypassing due to a plugged filter requiring achange.

The transmission neutralizer disabled indicator (2) is located in the center of the panel. Thisindicator is illuminated when the transmission neutralized is disabled.

The low fuel filter warning indicator (3) is located in the center row on the right side. Thisindicator is illuminated when the fuel level is below 10% of the total fuel tank volume.

The ride control SERVICE indicator (4) is located in the bottom row on left side. Thisindicator is illuminated when the ride control switch is placed in the SERVICE position.

The ride control AUTO indicator (5) is located in the bottom row, center. This indicator isilluminated when the ride control switch is placed in the AUTO position.

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Implement Control Valve - With Ride Control

The ride control system is an option on the 950H and the 962H Wheel Loaders. The optionalride control system provides a means for dampening the bucket forces which produce a pitchingmotion as the machine travels over rough terrain. The operation of ride control is initiated bythe switch input to the Power Train ECM with outputs to the solenoid valves on the implementcontrol valve (1).

On the implement control valve, there are two solenoid valves that control oil flow over theantidrift valves and one solenoid valve controlling the shifting of the balance valve. Theenergizing solenoid valve (2) provides a path of oil between the head end of the lift cylindersand the ride control accumulator. The energizing solenoid valve (3) allows the balance spool toshift as the solenoid valve provides a path for the oil on the end of the balance spool to flow tothe hydraulic tank passage. The energizing solenoid valve (4) drains the oil pressure off theantidrift valve enabling the valve to raise and allow oil to flow between the rod end of the liftcylinders and the hydraulic tank.

The optional rid

serv1824-950h-962h.pdf

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