Mitsubishi Galant 9G. Manual - part 1466

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-274

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 an open circuit has occurred in 
the wiring harness between the passenger’s air bag 
OFF indicator light and the SRS-ECU. If the vehicle 
condition returns to normal, DTC B1489 will be auto-
matically erased, and the passenger’s air bag OFF 
indicator 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-275

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-276

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 or B1543>, 

P.52B-321

 <B1545 or B1546>). 

NO :  Go to Step 4.

STEP 4 Using scan tool MB991958, check actuator test.

• Item No.03: Passenger’s air bag OFF indicator light illumi-

nation

Q: Does the passenger’s air bag indicator light illuminate 

or go out normally?
YES : Go to Step 5.
NO :  Relace the passenger’s air bag OFF indicator light 

(Refer to GROUP 52A, Instrument Panel Assembly 

P.52A-3

). Then go to Step 6.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-277

STEP 5. Check the harness between SRS-ECU connector 
C-121 (terminal No.21) and passenger’s air bag OFF 
indicator light C-06 (terminal No.3).

• Check the passenger’s air bag OFF indicator light output 

lines for open circuit.

NOTE: After inspecting intermediate connector C-22 inspect 
the wiring harness. If intermediate connector C-22 is damaged, 
repair or replace them. Refer to GROUP 00E, Harness Con-
nector Inspection . Then go to Step 6.

Q: Is the check result satisfactory?

YES : Erase the diagnostic trouble code memory, and check 

the diagnostic trouble code. If DTC B1489 sets, 
replace the SRS-ECU (Refer to 

P.52B-365

). Then go 

to Step 6.

NO :  Repair the harness wires. Then go to Step 6.

AC305233CX

CONNECTOR: C-06

HARNESS SIDE

AC305362

CONNECTOR: C-121

C-121 (Y)

AH

SRS-ECU

C-121
HARNESS SIDE 
CONNECTOR
(REAR VIEW)

42

31

38

27

21

41

28

39

22

30

25

47

36

33

44

34

45

37

48

26

29

23

40

32

43

35

46

24

B

A

AC305233 AI

CONNECTOR: C-22

C-22 (Y)