YYou’re probably already awareof just how stringent the rulesfor air quality are here in
California. Chances are you also knowthat no matter what laws they pass orwhat rules they put in place, the smog isstill going to be with us.
What you may not be familiar withis what some manufacturers are doingto help alleviate these conditions… andhow drivability diagnosis just got a lit-tle tougher, because of today’s OBD-IIregulations. We’re seeing more andmore driveability problems on theATRA HelpLine; what’s surprising ishow few technicians really understandtoday’s On-Board Diagnostic systems,and how they affect powertrain opera-tion. In this issue of Let’s Play Ball,we’ll cover some of the definitions andchanges to the OBD-II rulebook, andhow those new rules are making it hard-
er and harder to hit one out of the diag-nostic park.
The Facts about OBD-IIThe California Air Resources
Board (CARB) began regulation of OnBoard Diagnostic II (OBD-II) for dieselvehicles sold in California beginningwith the 1997 model year. In reality,OBD-II first began showing up in gaso-line-powered passenger cars in 1994.
OBD-II requires today’s vehiclecomputers to monitor all emission-related components (fig 1). TheMalfunction Indicator Lamp (MIL) hasto light and alert the driver of the needfor service to the emission control sys-tem. A Diagnostic Trouble Code (DTC)is associated with the MIL, identifyingthe specific area of the fault. Today, theOBD-II system is required for all vehi-cles under 14,000 GVW — gas and
diesel.The OBD-II system meets govern-
ment regulations by monitoring theemission control system. Generallyspeaking, when a system or componentfails or goes far enough out of range tocause the vehicle to exceed emissionthresholds, the computer lights the MILand stores a DTC in memory.
Diagnostic Trouble Codes (DTCs)Here’s how OBD-II systems moni-
tor and indicate system faults. Thecomputer monitors the system for faultsduring a drive cycle — a specific seriesof operating conditions (more aboutdrive cycles later):
• The first time the computer detects aproblem, it sets a pending DTC inthe computer’s keep-alive RandomAccess Memory (RAM).
24 GEARS August 2004
ON-BOARD DIAGNOSTICSFOR THE FORD DIESELON-BOARD DIAGNOSTICSFOR THE FORD DIESEL
LETS PLAY BALL
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• After two consecutive drive cycleswith the fault present, the computerturns the MIL on and sets a DTC.
• Once a monitor lights the MIL, thevehicle must go through three con-secutive drive cycles without thefault for the MIL to turn off.
• The computer clears the DTC auto-matically after 40 drive cycles with-out the fault appearing, once the MILis turned off.
The OBD-II diagnostic computerprogram in vehicle computer coordi-nates the OBD-II self-monitoring sys-tem. This program controls all monitorsand interactions, DTC and MIL opera-tion, freeze frame data, and scan toolinterface.
Freeze Frame is a valuable diag-nostic tool that captures scan data at themoment the computer stores the first
DTC in memory. This data is accessiblewith the scan tool to assist in repairingthe condition that cause the DTC to set.
OBD-II Inspection andMaintenance (IM) readiness DTCP1000 indicates that not all of the OBDmonitors have been completed since thecomputer’s keep-alive RAM was lastcleared. In some states, it may not bepossible to obtain vehicle registrationor pass an emission’s inspection ifP1000 is still in memory. To erase DTCP1000, operate the vehicle through themanufacturer’s specified drive cycle,until the computer goes through a fullset of monitors and identifies propersystem operation.
Drive CyclesSpecific drive cycles can vary
between manufacturers and systems(Fig 2). OBD-II standards for a drive
cycle include:1. Start and warm the engine to approx-
imately 180ºF (ECT at 180°F for atleast 4 minutes).
2. Let the vehicle idle for 45 seconds. 3. From a stop, accelerate to 45 mph at
1/4 throttle; about 10 seconds.4. Steady throttle between 30-40 MPH
for 60 seconds.5. Drive 20-40 MPH (no WOT) for
about 4 minutes.6. Decelerate to a stop and idle for 10
seconds.7. Accelerate to 55 MPH at 1/2 throttle;
about 10 seconds8. Steady the throttle between 40-60
MPH, posted speed limit for 80 sec-onds.
The specific order and duration ofthese conditions will vary from manu-facturer to manufacturer.
GEARS August 2004 25
PART 1PART 1
by Lance Wiggins
Figure 1 – All of these are systems in the vehicle.All of them have monitors
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26 GEARS August 2004
OBD-II System MonitorsThe OBD-II systems monitors
include:• OBD-II Trip Monitor• Comprehensive Component Monitor
• Glow Plug Monitor• Misfire Detection Monitor• Exhaust Gas Recirculation (EGR)
Monitor• Catalyst Converter Monitor
As you can see, OBD-II provides
many different ways to identify a sys-tem failure, as long as all the stars arelined up… but what happens whenthey’re not?
In the 2001 ATRA technical semi-nar, we discussed codes P0603 (RAM)
On-Board Diagnostics for the Ford Diesel, Part 1
Figure 2
Comprehensive Component and EGR Monitor
DriveInstruction
Start andWarm Eng.
ECT @180oF
IdleAccel.
to 45 MPH1/4 Throttle
SteadyThrottle
30-40 MPH
Drive20-40 MPH(No WOT)
DecelandIdle
Accelto 55 MPH1/2 Throttle
SteadyThrottle
40-60 MPHPostedSpeed
TimeAt Least
4 minutes
OBD-II Trip
OBD-II DRIVE CYCLE
Misfire and Adaptive Fuel Monitors
Catalyst Efficiency M
onitor
HO2S Monitors
45 Seconds 10 Seconds 60 Seconds 4 Minutes 10 Seconds 10 Seconds 80 Seconds
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GEARS August 2004 27
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Random Access Memory failure andP0605 (KAM) Keep Alive Memoryfailure. If any one of these codes ispresent, there’s a good chance youwon’t be able to get codes from thecomputer because of a memory loss.Something else that can interfere withOBD-II monitors and codes is if thecomputer isn’t receiving the proper
voltage, because of aftermarket deviceslike CB radios, police scanners or aux-iliary lighting. When a failure is presentand you can’t get codes from the com-puter, it’s time to monitor the differentareas of the OBD-II system.
In the next issue of GEARS, we’llcover the comprehensive diagnosticmonitors and how they relate to the
daily driving habits of your customer…and That’s the Game!
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