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SRS

Published by Chonan Technical Service Training Center

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Objectives To know the system components of SRS system.

To understand the handling caution and replacement items for SRS system.

The SRS system for ED vehicle has an ACU supplied and developed by ‘TRW Gen 5.6’. This

ACU already introduced in VQ so please refer to VQ training manual for more detail information. This manual will handle just for the basic information includes the parts components, its location

and some tips for warning lamp driving.

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1. Introduction

1.1 Major Components - ACU: Airbag Control Unit (TRW GEN 5.6)

- FIS: Front Impact Sensors (LH & RH)

- SIS: Side Impact Sensors (LH & RH – front only)

- DAB: Single stage de-powered Driver Airbag Module

- PAB: Single stage de-powered Passenger Airbag Module

- SAB: Side Airbag (LH & RH - Front only)

- CAB: Curtain Airbag

- SPT: Seatbelt Pre-Tensioner with load limiters

- PAD (Passenger Airbag Deactivation) Switch – EU only

Depowered Airbag System (EU)

2. Component and Function 2.1 ACU(Airbag Control Unit)

ED Car has a MOBIS-TRW Gen 5.6 Airbag Electronic Control Unit (ACU). The ACU is designed to handle the “Depowered” functionality.

CAB

SAB

Single-PAB

Single-DAB

SIS

ACU

PAD S/W

Seat Belt Pre-tensioner

FIS

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Function :

- Crash Detection

- Activation of the front airbags, Curtain airbags and belt pre-tensioners

- Monitoring of the airbag restrain system

- Indicate system readiness and faults to the driver by means of a fault warning lamp

- Facilitate servicing capability via a serial diagnostic communication interface (scanner)

After power ON, the ACU shall behave as follows: a) In the power OFF region, the ACU shall not perform any external and internal diagnostic since

the operation of the ACU is not guaranteed. If the ACU is operational, it shall attempt to command the AWL ON.

b) The ACU shall perform internal diagnostics only if thirty consecutive (10ms sample rate) voltage reading are within or above the “Vbatt too low” range. If the ACU doesn’t detect a voltage reading within the “normal operating range” for 4sec, then “Vbatt too low” or “Vbatt too high” is qualified.

c) The ACU shall perform external diagnostics only if thirty consecutive (10ms sample rate) voltage readings are within the “normal operating” range.

ACU shall try to deploy corresponding firing squib(s) in case of crash detection during power disturbance region.

Operational Temperature: -40 to 85 °C Storage Temperature: -40 to 90 °C

Connector PIN Layout :

13 14 15 16 17 18 19 20 21 22 23 24 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

1 2 3 4 5 6 7 8 9 10 11 12 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17

Shorting bar clipConnector A Connector B

Pin Assignment : Cavity A (J1A-XX) Cavity B (J1B-XX) AECU

Pin # (IP) ACEU Pin # (Body)

1 Ignition 1 Squib_9_L / Drv Side 2 ISO9141 (K-Line) / CANH 2 Squib_9_H / Drv Side 3 CANLO 3 Squib_10_H / Pass Side 4 SeatBelt Reminder 4 Squib_10_L / Pass Side 5 Crash Out 5 Squib_12_L / Pass curtain 6 PAD Lamp 1 6 Squib_12_H / Pass curtain

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7 Unused (GND) 7 Squib_11_H / Drv curtain 8 DSI_CHANNEL2- FIS Pass LOW 8 Squib_11_L / Drv curtain 9 DSI_CHANNEL2+ FIS Pass HIGH 9 Squib_13_L / Drv Rear curtain 10 DSI_CHANNEL1- FIS Drv LOW 10 Squib_13_H / Drv Rear curtain 11 DSI_CHANNEL1+ FIS Drv HIGH 11 Squib_14_H / Pass Rear Curtain 12 PAD Switch 12 Squib_14_H / Pass Rear Curtain 13 AIRBAG WARNING LAMP 13 Squib_3_L / Drv Frontal Pret 14 GND 14 Squib_3_H Drv Frontal Pret 15 Squib_2_L / Passenger 1st Stage 15 Squib_4_H Pass. Frontal Pret 16 Squib_2_H / Passenger 1st Stage 16 Squib_4_L Pass. Frontal Pret 17 Squib_1_H / Driver 1st Stage 17 DR_BUCKLE sensor 18 Squib_1_L / Driver 1st Stage 18 PASS_BUCKLE 19 Squib_8_L / Passenger 2nd 19 DRV Seat Position 20 Squib_8_H / Passenger 2nd Stage 20 PASS Seat Position 21 Squib_7_H / Driver 2nd Stage 21 DSI_CHANNEL3- SIS Drv LOW 22 Squib_7_L / Driver 2nd Stage 22 DSI_CHANNEL3+ SIS Drv HIGH 23 Squib_16_H / Drv rear Side 23 DSI_CHANNEL4- SIS Pass LOW 24 Squib_16_L / Drv rear Side 24 DSI_CHANNEL4+SIS Pass HIGH

25 Unused (GND) 26 Occupant Classification(ISO9141) 27 Squib_15_H / Pass Rear Side 28 Squib_15_L / Pass Rear side 29 Squib_5_L / Drv 2nd Stage Pret 30 Squib_5_H Drv 2nd Stage Pret 31 Squib_6_H / Pass 2nd Stage Pret 32 Squib_6_H / Pass 2nd Stage Pret

Connector shorting bar present

Grey ZonePower off Guaranteed Range Grey

ZoneVbatt

too highVbatt

too lowGrey Zone

8.02 8.99 16.05 17.635.19 5.95

Normal Operating Range

4 sec4 sec4 sec4 sec

“Vbatt too low”DTC dequalified

“Vbatt too low”DTC qualified

“Vbatt too high”DTC qualified

“Vbatt too high”DTC dequalified

A/D Count = 164A/D Count = 79A/D Count = 49

Grey ZonePower off Guaranteed Range Grey

ZoneVbatt

too highVbatt

too lowGrey Zone

8.02 8.99 16.05 17.635.19 5.95

Normal Operating Range

4 sec4 sec4 sec4 sec4 sec4 sec4 sec4 sec

“Vbatt too low”DTC dequalified

“Vbatt too low”DTC qualified

“Vbatt too high”DTC qualified

“Vbatt too high”DTC dequalified

A/D Count = 164A/D Count = 79A/D Count = 49

Range Name Nominal voltage Fault Qualification/Dequalification

Power off Ign < 6 Qualification/Dequalification of all internal and external DTC’s are suspended (qualification / dequalification counter frozen)

Vbatt too low 6 < Ign < 9 • Qualification/Dequalification of external DTC’s are performed normally until “Vbatt too low” DTC is qualified.

• Qualification/Dequalification that are performed regardless of Ignition voltage level in this range

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consist of DTC related to: 1. RAS diagnostics 2. Internal diagnostics 3. Crash related 4. SIFA inputs

• OCE communication DTC qualification/dequalification are disabled as soon as ignition is detected in this range without waiting for “Vbatt too low” to be qualified.

Normal Operating range

9 < Ign < 16 Qualification/Dequalification of all internal and external diagnostics are performed normally in this range.

Note: Ignition has to be in this range for 3s (± 10%) before OCE communication Qualification/Dequalification diagnostics are performed.

Vbatt too high Ign > 16 • Qualification/Dequalification of external DTC’s are performed normally until “Vbatt too hi” DTC is qualified.

• Qualification/Dequalification that are performed regardless of Ignition voltage level in this range consist of DTC related to:

1. RAS diagnostics 2. Internal diagnostics 3. Crash related 4. SIFA inputs

2.2 Frontal Airbags

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Resistance (Ω): 1.7~2.3 (for both DAB & PAB)

2.4 SAB (Side Air Bag) & CAB (Curtain Airbag)

Resistance (Ω): 1.7~2.3 (for both SAB & CAB)

2.5 SPT(Seatbelt Pre Tensioner) When a vehicle has crashed with a certain

degree of frontal impact, the gas generator is

made to ignite by the electrical firing signal from

SRSCM. Gas from the gas generator causes

movement of the piston in the manifold case

(cylinder), which operates a rack gear. Finally

the webbing is retracted by the rotation of the

spool. Therefore the seat belt pretensioner

helps to reduce the severity of injury to he front

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occupant by retracting the seat belt webbing to

prevent the occupant from moving forward and hitting the steering wheel or instrument panel when

the vehicle is crashed. On the other hand, the buckle pre-tensioner is not applied in ED.

2.6 FIS (Front Impact Sensor) & SIS(Side Impact Sensor) The front impact sensor (FIS) is installed on the upper of the side panel in Front End Module (FEM).

They are remote sensors that detect acceleration due to a collision at its mounting location. The primary purpose of the Front Impact Sensor (FIS) is to provide an indication of a collision. The Front Impact Sensor(FIS) sends acceleration data to the SRSCM. The Side Impact Sensor (SIS) system consists of two front SIS which are installed in the center pillar

(LH and RH) and two rear SIS which are installed in the rear pillar (LH and RH). They are remote sensors that detect acceleration due to collision at their mounting locations. The primary purpose of the Side Impact Sensor (SIS) is to provide an indication of a collision. The Side Impact Sensor (SIS) sends acceleration data to the SRSCM.

TRW-RASII (Remote Acceleration Sensor) The RASII shall be used as a remote crash sensing

module providing acceleration and status data over

the DSI bus to the ACU. The main components of

RASII assembly are the 250 acceleration sensor and

the Orion ASIC. This ASIC provides power for the

accelerometer and for itself, accelerometer

measurement and communication between the

remote acceleration sensor and the central air bag

control module in the vehicle.

The Orion ASIC obtains analog data from the

Sensor Part for SIS (TRW RAS II)

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accelerometer, converts it to digital information, and

then transmits the acceleration data over the DSI

interface bus when commanded by the central air bag

control module in the vehicle.

The RASII is intended to directly interface with a DSIP ASIC inside the ACU. Power and data

communications are performed on one interface conductor between the RASII and ACU. A second

common / ground conductor completes the interface. For 4 pin RASII a second set of Power /

Communications and common / ground conductors are used to interface to a second RASII.

RASII Locations and Acceleration Ranges

RAS Application Location Options Axis Accel. Range

Options Frontal impact crush zone sensor Frontal Impact Crush Zone ± x axis ± 250g

Side impact Crush Zone ± z axis ± 250g

RASII component block diagram

. 2.8 PAD (Passenger Airbag Deactivation) Switch

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(1) Purpose for Installation The PPD sensor used for detecting that any passenger is or not in convention is removed. Instead, the ON/OFF S/W is installed inside of the glove box, so that the driver can determine that the PAB may be unfold or not.

The ACU shall be capable of sensing the following PAD switch status:

1. PAD switch in enable position

2. PAD switch is disable position

3. PAD switch unstable

4. Open / Short to Battery

5. Short to Ground

Co

BODY HOUSING

COVER

REAR COVER

ROTOR PCB

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nnector type and pin Layout

SPRING HOLDER

Pin No Description1 Ignition 12 Earth- Glove Box3 Ground – ACU I/F

4 ACU Interface Line

ing Center

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PAB ON/OFF SWITCH WIRE DIAGRAM

(2) PAD switch Resistive Load

The ACU shall sample the PAD switch

periodically(50ms). The ACU shall change

the status of PAD switch only after 5

consecutive samples with a status change

have been received. If a stable input is not

achieved within 20 samples, then instability

DTC shall be qualified.

The ACU shall be capable of sensing the following PAD switch statuses: 1. PAD switch in enable position 2. PAD switch is disable position 3. PAD switch instable 4. Open/ Short to Battery

PAD Switch Status Resistances between PIN #3 and #4

Enabled 1010 ohm ± 10%

Disabled 330 ohm ± 10%

5. Short to Ground 6. Defect

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4. Electrical Interface Requirements 4.1 Squibs The ACU is designed to provide electrical energy back up a maximum 12 squibs for up to 150msec.

This allows for a maximum of one squib shorted.

4.2 squib wires shorted to GND If any one of the twelve squibs that are protected by backup energy is shorted to ground, sufficient

energy will still be provided to the other eleven squibs to maintain firing capability.

4.3 GEN 5.6 Firing Loops & Diagnosis Currents The ACU shall be capable to deploy all backed up firing loops up to at least 150ms after IGN has

been disconnected. The firing and diagnostic current requirements for a specific platform is defined in corresponding application addendum.

4.5 Squib Diagnostics The ACU shall be capable of detecting when any of the squibs are shorted to battery or ground, or

open circuit. The ACU shall record such a condition. The largest current that the ACU will pass through the squib is the pulse used for measuring the resistance of the squib and wiring. The level of the pulse corresponds to 20mA to 32mA. Based on a good squib range of 1.6ohms to 6.1 ohms (worst case), this will give a differential voltage across to squib of 32mV to 195mV. The ACU will pass other smaller current pulse to diagnose faults of the squib ASIC, and their interconnections.

5. Outputs 5.1 Airbag (SRS) Warning Lamp Operations

(Active fault or historical fault counter is greater or equal to 10)

(Normal or historical fault counter is less than 10) During start-up phase, the warning lamp shall be commanded ON for 6 seconds (+/- 10 %) and

OFF for 1 second. Thereafter, the lamp shall be commanded ON only under the following cases:

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1. Lamp latch condition 2. Qualified fault is present 3. During communication with service tool.

5.2 SRS Warning Lamp latch The SRS warning lamp shall be latched ON if certain conditions are present. Some lamp latch

conditions can be cleared by the service tool while others require the replacement of the ACU.

Below is a description of each condition:

Lamp Latch condition that can be cleared by the service tool:

1. 10 different external faults except Vbatt too low are qualified in the ACU.

2. A certain external fault except Vbatt too low has qualified 10 times in the ACU.

3. Belt pretensioner only firing (<6 times)

4. Rear crash detected DTC is qualified

5. Instability DTC for Seat Buckle, Seat Position, and PAD Switch.

Lamp Latch condition that can not be cleared by the service tool.:

1. Any internal DTC is qualified.

2. Belt pretensioner only firing (≥6 times)

3. Any airbag deployment DTC is qualified

5.3 ACU behavior during service communication During the service or repair communication process the ACU shall behave as follows:

ACU shall turn its SRS warning lamp ON as long as the communication between ACU and Service

tool is active. . . . .

Internal diagnostics process of ACU and external diagnostic process of related system shall not be

altered and shall be carried out as it is in normal operating condition.

1. The crash discrimination and firing shall be suppressed to prevent inadvertent deployment

during service communication.

The SRS warning lamp shall not be turned OFF even though stored faults memory is erased via

service tool unless the communication process is completed or terminated.

The ACU shall consider the communication process as completed if:

1. A stop communication request from service tool is received

2. The communication is timed out (300 ms)

Under the above conditions, the ACU shall reset without supply power on/off. The SRS warning

lamp shall go through normal Phase-up.

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5.4 Passenger Airbag Disable (PAD) Indicator Operation The ACU shall be designed with circuitry and software to drive either a PAD or a tell-tale lamp.

PAD lamp will be used for de-powered systems. For the PAD indicator circuitry to function properly

both the ACU and PAD Indicator shall be sourced from the same ignition line.

During phase-up, the PAD indicator shall be commanded ON for 4 seconds (+/- 10 %) and OFF for 3 second. Thereafter the lamp will be turned on as long as the PAD switch is in the disabled position.

PAD Lamp operation during Phase-up

5.5 Crash Output When a deployment occurs, or when a rear crash is detected, the Crash Output is activated. The

Crash Output will have the capability to sink a minimum of 15 mA to ground from Vbatt, and a 1.2

kΩ source or from Vcc and a 470 Ω source, under normal operating conditions. The waveform of

the output will be to activate the output within 100 ms (± 10%) of the airbag or pretensioner

deployment, or rear crash detection and hold the output for 200 ms, ± 10%. The purpose of this

output is to signal the BCM/ETAC module in the vehicle to unlock the vehicle doors. If a crash

output signal is in progress, a second crash output signal will not be sent unless the first one is

completed.

The ACU doesn’t perform diagnostics on the crash output function. In addition, the failure

handlings such as circuit failure between ACU and BCM, noise injection in crash output command

line that may induce invalid message shall be handled by BCM not ACU

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Crash Output Signal

Crash Output interface to the ACU

6. System Diagnostics and Fault Handling 6.1 Fault Recognition The ACU shall start the fault management during the prove-out period. The ACU qualifies a fault

when it has detected that fault for the qualification period or number of occurrences. The ACU shall

store the fault codes onto EEPROM and turn ON the SRS warning lamp. RAS sensor fault are tested

at a more rapid rate than other faults ; their sample rate is based on the algorithm update rate. Some

internal fault are only tested during phase-up.

After a fault is qualified, the fault is de-qualified when that fault has been not detected for the de-

qualification period. If no qualified faults are present, the warning lamp turns off. Diagnosis of firing

devices is suspended during the deployment process, but resumes thereafter. Faults for devices

which were fired in a crash will be suppressed.

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6.2 Fault Handling An internal fault is a fault inside of the ACU (i.e. accelerometer, microcomputer power supply, or

watch dog),and is not erasable. An external fault is a fault outside of the ACU (i.e. RAS II, Occupant

Detection, squibs), and is erasable. Once any internal fault has been qualified, the corresponding fault

record in non-volatile memory of the ACU shall not be erasable. All internal faults shall not de-qualify.

The ACU denounces all faults to make sure that no erroneous faults are recorded. The ACU shall

set qualified faults to historic faults as soon as the active fault conditions are recovered and

disqualified. At this time, the warning lamp shall be turned off and historic fault code and

corresponding fault information shall be stored in EEPROM within the ACU.

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