Mitsubishi Galant 9G. Manual - part 1416

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-74

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-75

STEP 3. Check the front impact sensor (RH) power supply 
circuit. Measure the voltage at the front impact sensor (RH) 
connector A-27.
(1) Disconnect the negative battery terminal.
(2) Disconnect front impact sensor (RH) connector A-27, and 

measure at the wiring harness side.

(3) Connect the negative battery terminal.
(4) Turn the ignition switch to the "ON" position.

CAUTION

Do not insert a test probe into the terminal from its front 
side directly, as the connector contact pressure may be 
weakened.
(5) Measure the voltage between A-27 harness side connector 

terminal 2 and ground.
Voltage should measure 9 volts or more

Q: Is the measured voltage within the specified range?

YES : Replace the front impact sensor (RH) (Refer to 

P.52B-362

). Then go to Step 5.

NO :  Go to Step 4.

STEP 4. Check the harness wires for open circuit or short 
circuit between SRS-ECU connector C-121 (terminal No.47 
and 48) and front impact sensor (RH) connector A-27 
(terminal No.1 and 2).

AC305206

A-27 (Y)

HARNESS SIDE

BA

CONNECTOR: A-27

AC308161

A-27 HARNESS SIDE
CONNECTOR
(REAR VIEW)

AB

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

AC305206

A-27 (Y)

HARNESS SIDE

BA

CONNECTOR: A-27

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-76

NOTE: After inspecting intermediate connectors C-22 and C-11 
inspect the wiring harness. If the intermediate connectors C-22 
and C-11 are damaged, repair or replace it.

Q: Are the harness wires between SRS-ECU connector 

C-121 (terminal No.47 and 48) and front impact sensor 
(RH) connector A-27 (terminal No.1 and 2) in good 
condition?
YES : Erase the diagnostic trouble code memory, and check 

the diagnostic trouble code. If DTC B1407 sets, 
replace the SRS-ECU (Refer to 

P.52B-365

). Then go 

to Step 5.

NO :  Replace the harness wires between SRS-ECU 

connector C-121 and front impact sensor (RH) 
connector A-27. Then go to Step 5.

STEP 5. 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 DTC B1407 set?

YES : Return to Step 1.
NO :  The procedure is complete.

AC305233 AI

CONNECTOR: C-22

C-22 (Y)

AC305233CN

CONNECTOR: C-11

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-77

DTC B1408: Front Impact Sensor (RH) (Squib) for Power Supply Circuit
DTC B1409: Front Impact Sensor (RH) (Squib) for Communication System

CAUTION

If DTC B1408 or B1409 is set in the SRS-ECU, 
always diagnose the CAN main bus line.

.

Front Impact Sensor Circuit

INTERFACE CIRCUIT

SRS-ECU

FRONT IMPACT
SENSOR (LH)

FRONT IMPACT 
SENSOR (RH)

AC305206

A-27 (Y)

BC

CONNECTOR: A-27

AC305233CV

CONNECTOR: C-11

AC305233 AO

CONNECTOR: C-22

C-22 (Y)

AC305362

CONNECTOR: C-121

C-121 (Y)

AD

SRS-ECU