Mitsubishi Galant 9G. Manual - part 1464

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-266

CAUTION

If DTC B1489 is set in the SRS-ECU, always diag-
nose the CAN main bus line.

.

CIRCUIT OPERATION

• Power for the passenger’s air bag OFF indicator 

light is supplied from the ignition switch (IG1).

• The passenger’s air bag OFF indicator light illu-

minates when the ignition switch is turned to the 
"ON" position and goes out after approximately 
seven seconds if there is not a malfunction in the 
SRS system.

• If a failure occurs in the system, the SRS-ECU 

will stop sending that SRS warning light "OFF" 
signal, thus causing the combination meter to illu-
minate the SRS warning light.

• The SRS warning light "OFF" signal is not sent to 

the combination meter in the cases below, either. 
Therefore, the combination meter will illuminate 
the SRS warning light.

• The SRS-ECU connector is disconnected.

• The SRS-ECU is not working normally due to 

a failure in its power supply lines.

• The wiring harness between the passenger’s 

air bag OFF indicator light and the SRS-ECU 
is broken.

.

DTC SET CONDITIONS

This DTC will be set if the passenger’s air bag OFF 
indicator light driving circuit is short to ground. If the 
vehicle condition returns to normal, DTC B1489 will 
be automatically erased, and the warning light will go 
out.

.

TROUBLESHOOTING HINTS

• Damaged wiring harnesses or connectors

• Malfunction of the SRS-ECU

• Malfunction of the passenger’s air bag OFF indi-

cator light

.

DIAGNOSIS

Required Special Tools:

•  MB991958: Scan Tool (MUT-III Sub Assembly)

• MB991824: Vehicle Communication Interface (V.C.I.)

• MB991827: MUT-III USB Cable

• MB991910: MUT-III Main Harness A (Vehicles with CAN 

Communication System)

AC305233CW

CONNECTOR: C-06

AC305233 AO

CONNECTOR: C-22

C-22 (Y)

AC305362

CONNECTOR: C-121

C-121 (Y)

AD

SRS-ECU

AC305415

CONNECTORS : C-211, C-215

C-211

C-215

AZ

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-267

STEP 1. Using scan tool MB991958, diagnose the CAN bus 
line.

CAUTION

To prevent damage to scan tool MB991958, always turn the 
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958. Refer to "How to connect the 

scan tool 

P.52B-30

."

(2) Turn the ignition switch to the "ON" position.
(3) Diagnose the CAN bus line.
(4) Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the CAN bus line found to be normal?

YES : Go to Step 2.
NO :  Repair the CAN bus line (Refer to GROUP 54C, 

Diagnosis ).

STEP 2. Recheck for diagnostic trouble code.
Check again if the DTC is set.
(1) Erase the DTC.
(2) Turn the ignition switch to the "ON" position.
(3) Check if the DTC is set.
(4) Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the DTC set?

YES : Go to Step 3.
NO :  There is an intermittent malfunction such as poor 

engaged connector(s) or open circuit (Refer to 
GROUP 00, How to Use Troubleshooting/Inspection 
Service Points 

− How to Cope with Intermittent 

Malfunctions ).

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-268

STEP 3. Using scan tool MB991958, read the diagnostic 
trouble code.

CAUTION

To prevent damage to scan tool MB991958, always turn the 
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Turn the ignition switch to the "ON" position.
(2) Check if the DTC is set.
(3) Turn the ignition switch to the "LOOK (OFF)" position.

Q: Is DTC B1540, B1541, B1542, B1543, B1545 or B1546 

set?
YES : Carry out the troubleshooting of the occupant 

classification-ECU or the occupant classification 
sensor system (Refer to 

P.52B-319

 <B1540, B1541, 

B1542, B1543>, 

P.52B-321

 <B1545, B1546>). 

NO :  Go to Step 4.

STEP 4. Check the passenger’s air bag OFF indicator light 
connector C-06.
Q: Is the connector correctly engaged?

YES : Go to Step 5.
NO :  Engage the connector correctly. Then go to Step 10.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AC305233CX

CONNECTOR: C-06

HARNESS SIDE

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-269

STEP 5. Measure the voltage at passenger’s air bag OFF 
indicator light connector C-06.
(1) Disconnect passenger’s air bag OFF indicator light 

connector C-06.

(2) Measure the voltage between C-06 harness side connector 

terminal 1 and body ground.
Voltage should measure approximately 12 volt.

Q: Is the check result satisfactory?

YES : Go to Step 7.
NO :  Go to Step 6.

STEP 6. Check the harness for short circuit between 
ignition switch connector C-308 (terminal No.2) and 
passenger’s air bag OFF indicator light C-06 (terminal 
No.1).

AC305233CX

CONNECTOR: C-06

HARNESS SIDE

AC308205

C-06 HARNESS SIDE
CONNECTOR

AB

AC305235AG

CONNECTOR: C-308

C-308

2
5

4

1

6

3

AC305233CX

CONNECTOR: C-06

HARNESS SIDE