Mitsubishi Galant 9G. Manual - part 1427

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-118

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 ).

STEP 3. Check for any diagnostic trouble code. (Using 
scan tool MB991958, read the diagnostic trouble code.)
Check the front impact sensor (LH).
(1) Disconnect the negative battery terminal.
(2) Replace the front impact sensor (LH) with the front impact 

sensor (RH).

(3) Connect the negative battery terminal.
(4) Erase diagnostic trouble code from memory, and check the 

diagnostic trouble code.

Q: Is DTC B1408 or B1409 set?

YES : Replace the front impact sensor (LH) with a new one 

(Refer to 

P.52B-377

). Then go to Step 5.

NO :  Go to Step 4.

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-119

STEP 4. Check the harness wires for open circuit or short 
circuit between SRS-ECU connector C-121 (terminal No.38 
and 39) and front impact sensor (LH) connector A-23 
(terminal No.1 and 2).

NOTE: After inspecting intermediate connectors C-22 and C-29 
inspect the wiring harness. If the intermediate connectors C-22 
and C-29 is damaged, repair or replace it.

Q: Are the harness wires between SRS-ECU connector 

C-121 (terminal No.38 and 39) and front impact sensor 
(LH) connector A-23 (terminal No.1 and 2) in good 
condition? 
YES : Erase the diagnostic trouble code memory, and check 

the diagnostic trouble code. If DTC B1418 or B1419 
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 (LH) 
connector A-23. Then go to Step 5.

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

AC305210

CONNECTOR: A-23

AT

A-23 (Y)

HARNESS SIDE

AC305233 AI

CONNECTOR: C-22

C-22 (Y)

AC305231AI

CONNECTOR: C-29

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-120

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 B1418 or B1419 set?

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

DTC B1420: Side-Airbag Module (RH) (Squib) System Fault 1 (Short Circuit between Terminals of the 
Squib Circuit)

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

SIDE AIR BAG
MODULE
(SQUIB) (RH)

AIR BAG DRIVE CIRCUIT

SRS-ECU

CONNECTOR
LOCK SWITCH

CONNECTOR
LOCK SWITCH

Side-Airbag Module (RH) (Squib) Circuit

NOTE
  : CONNECTOR
    CONNECTED
    : ON
    CONNECTOR
    DISCONNECTED
    : OFF

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-121

CAUTION

If DTC B1420 is set in the combination meter, 
always diagnose the CAN bus lines.

.

CIRCUIT OPERATION

• The SRS-ECU judges how severe a collision is 

by detecting signals from the left and right side 
impact sensors. If the impact is over a predeter-
mined level, the SRS-ECU sends an ignition sig-
nal. At this time, if the side-airbag safing 
G-sensor is on, the SRS side-airbag will inflate.

• The ignition signal is input to the side-airbag 

module to inflate the side-airbag.

.

DTC SET CONDITIONS

This DTC is set if there is abnormal resistance 
between the input terminals of the side-airbag mod-
ule (RH) (squib).

.

TROUBLESHOOTING HINTS

• Improper engaged connector or defective short 

spring*

• Short between the side-airbag module (RH) 

(squib) circuit terminals

• Damaged connector(s)

• Malfunction of the SRS-ECU

NOTE: *: The squib circuit connectors integrate a 
"short" spring (which prevents the air bag from 
deploying unintentionally due to static electricity by 
shorting the positive wire to the ground wire in the 
squib circuit when the connectors are disconnected) 
(Refer to 

P.52B-3

). Therefore, if connector C-120 or 

D-32 is damaged or improperly engaged, the short 
spring may not be released when the connector is 
connected.

.

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)

• MB991865: Dummy resister

• MB991866: Resister harness

AC305362

CONNECTOR: C-120

C-120 (Y)

AC

SRS-ECU

AC307779

D-32 (R)

AC

CONNECTOR : D-32