Mitsubishi Galant. Manual — part 604

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM(SRS)

52B-57

CIRCUIT OPERATION

•

The SRS-ECU is powered from the ignition
switch (IG1).

•

The SRS-ECU power is supplied from two
circuits. Even if one circuit is shut off, the air bag
can inflate.

•

The SRS system diagnosis can be done by
connecting scan tool MB991502 to the data link
connector.

•

The SRS-ECU judges how severe a collision is
by detecting signals from the left and right side
impact sensors and the analog G-sensor. If the
impact is over a predetermined level, the SRS-
ECU outputs an ignition signal. At this time, if the
safing G-sensor is on, the SRS air bag will inflate.

TECHNICAL DESCRIPTION (COMMENT)

•

If communication is not possible with the SRS
only, the cause is probably an open circuit in the
on-board diagnostic output circuit of the SRS or
in the power circuit (including ground circuit).

TROUBLESHOOTING HINTS

•

Damaged wiring harnesses or connectors

•

Malfunction of the SRS-ECU

DIAGNOSIS

STEP 1. Check the ground line at the SRS-ECU connector
C-44 by backprobing.
(1)Do disconnect the connector C-44.
(2)Check the continuity between terminal 3 and the ground by

backprobing.

Q: Is the resistance between terminal 3 and ground less

than 2 ohm?
YES : Go to Step 3.
NO : Go to Step 2.

AC003195AB

CONNECTOR: C-44

SRS-ECU

CENTER
REINFORCEMENT

AC003201AB

CONNECTOR: C-73, C-77

JUNCTION BLOCK (REAR)

C-73

C-77

AC003213AB

CONNECTOR: C-23

AC000368AD

C-44 CONNECTOR HARNESS SIDE VIEW

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM(SRS)

52B-58

STEP 2. Check the harness wires between SRS-ECU
connector C-44 and ground.
Q: Is the harness wires between SRS-ECU connector C-44

and ground in good condition?
YES : Go to Step 5.
NO : Repair them. Then go to Step 5.

STEP 3. Check the ignition switch (IG1) line at the SRS-
ECU connector C-44 by backprobing.
(1)Do disconnect the connector C-44.
(2)Turn the ignition switch to "ON" position.
(3)Measure the voltage between terminal 9 and the ground.

•

Voltage should be 9 volts or more

(4)Measure the voltage between terminal 12 and the ground

by backprobing.

•

Voltage should be 9 volts or more

Q: Is the voltage between terminal 9,12 and the ground 9 V

or more?
YES : Go to Step 5.
NO : Go to Step 4.

STEP 4. Check the harness wires between ignition switch
(IG1) and SRS-ECU connector C-44.
NOTE: After inspecting intermediate connectors C-73, C-77
inspect the wiring harness. If intermediate connectors C-73, C-
77 are damaged, repair or replace them. Refer to GROUP 00E,
Harness Connector Inspection

P.00E-2

. Then go to Step 6. If

harness wires are in good condition, go to Step 6. If any
harness wires between the ignition switch (IG1) and SRS-ECU
connector C-44 are damaged, repair them. Then go to Step 6.

Q: Are the harness wires between ignition switch (IG1) and

SRS-ECU connector C-44 in good condition?
YES : Go to Step 6.
NO : Repair them. Then go to Step 6.

AC003195AB

CONNECTOR: C-44

SRS-ECU

CENTER
REINFORCEMENT

AC000367AD

C-44 CONNECTOR HARNESS SIDE VIEW

AC003195AB

CONNECTOR: C-44

SRS-ECU

CENTER
REINFORCEMENT

AC003201AB

CONNECTOR: C-73, C-77

JUNCTION BLOCK (REAR)

C-73

C-77

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM(SRS)

52B-59

STEP 5. Check the harness wires between SRS-ECU
connector C-44 and data link connector C-23.
Q: Are the harness wires between SRS-ECU connector C-

44 and data link connector C-23 in good condition?
YES : Replace the SRS-ECU. Refer to

P.52B-65

. Then go

to Step 6.

NO : Repair them. Then go to Step 6.

STEP 6. Check symptoms.

Q: Does the scan tool communicate normally with the SRS

system?
YES : This diagnosis is complete.(If no malfunctions are not

found in all steps, an intermittent malfunction is
suspected. Refer to GROUP 00, How to Use
Troubleshooting/Inspection Service Points

−

How to

Cope with Intermittent Malfunction.)

NO : There is no action to be taken.

AC003195AB

CONNECTOR: C-44

SRS-ECU

CENTER
REINFORCEMENT

AC003213AB

CONNECTOR: C-23

SPECIAL TOOLS

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SUPPLEMENTAL RESTRAINT SYSTEM(SRS)

52B-60

SPECIA L TO O LS

M1524000700088

TOOL

TOOL NUMBER AND
NAME

REPLACED BY MILLER
TOOL NUMBER

APPLICATION

MB991502
Scan tool (MUT-II)

MB991496-OD

•

Reading diagnostic trouble
codes

•

Erasing diagnostic trouble
codes

•

Reading vehicle data for a
specific period

•

Reading erase times (Refer to
MUT-II operating instructions)

MB991223
A:MB991219
B:MB991220
C:MB991221
D:MB991222
Harness set
A:Test harness
B:LED harness
C:LED harness adapter
D:Probe

-

Checking the continuity and mea-
suring the voltage at the SRS-
ECU harness connector

MB991613
SRS check harness

MB991613

Checking the SRS electrical cir-
cuitry with a digital multi-meter

MB990803
Steering wheel puller

General service tool

Removal of steering wheel

MR372530
SRS air bag adapter
harness A

General service tool

Deployment of air bag module
(Driver's side) inside the vehicle

MB686560
SRS air bag adapter
harness B

General service tool

•

Deployment of air bag module
(Front passenger's side) inside
the vehicle

•

Deployment of air bag module
(Front passenger's side) out-
side the vehicle

MR203491 or MB628919
SRS air bag adapter
harness C

General service tool

Deployment of air bag module
(Driver's side) outside the vehicle

B991502

MB991223

A

D

C

B

AG

MB991613

MB990803

MR372530

MB686560

MB628919