Mitsubishi Galant (2004+). Manual - part 1540

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-53

STEP 5. Check the harness between the SRS-ECU 
connector C-121 (terminal No.11 and 12) and the clock 
spring connector C-307 (terminal No.3 and 4) for open 
circuit.

(1) Disconnect SRS-ECU connector C-121 and clock spring 

connector C-307.

CAUTION

Do not insert a test probe into the terminal from its front 
side directly, as the connector contact pressure may be 
weakened.
(2) Check for continuity between the following terminals. It 

should be less than 2 ohms.

<1st squib>

• SRS-ECU connector C-121 (terminal No.36) and the 

clock spring connector C-307 (terminal No.13)

• SRS-ECU connector C-121 (terminal No.37) and the 

clock spring connector C-307 (terminal No.14)

<2nd squib>

• SRS-ECU connector C-121 (terminal No.33) and the 

clock spring connector C-307 (terminal No.11)

• SRS-ECU connector C-121 (terminal No.34) and the 

clock spring connector C-307 (terminal No.12)

Q: Does continuity exist?

YES : Erase the diagnostic trouble code memory, and check 

the diagnostic trouble code. If DTC B1401 <1st 
squib> or B1481 <2nd squib> set, replace the 
SRS-ECU. (Refer to 

P.52B-365

). Then go to Step 6. 

NO :  Replace the harness wires between SRS-ECU 

connector C-121 and clock spring connector C-307. 
Then go to Step 6.

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

AC305235AK

C-307 (Y)

CONNECTOR: C-307

C-307 HARNESS
SIDE CONNECTOR

CLOCK
SPRING

11

12

13

14

11

14

13

12

AC308146

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

C-307
HARNESS SIDE
CONNECTOR
(REAR VIEW)

C-121HARNESS
SIDE CONNECTOR
(REAR VIEW)

AB

<1ST SQUIB>

11

14

13

12

AC308147

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

C-307
HARNESS SIDE
CONNECTOR
(REAR VIEW)

C-121HARNESS
SIDE CONNECTOR
(REAR VIEW)

AB

<2ND SQUIB>

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-54

STEP 6. 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 B1401 <1st squib> or B1481 <2nd squib> set?

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

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-55

DTC B1402: Driver's Air Bag Module (1st Squib) System Fault for Power Supply Circuit 
(Short-Circuited to Power Supply)
DTC B1482: Driver's Air Bag Module (2nd Squib) System Fault for Power Supply Circuit 
(Short-Circuited to Power Supply)

AIR BAG MODULE
(SQUIB)
(DRIVER'S SIDE)

CLOCK 
SPRING

AIR BAG DRIVE CIRCUIT

SRS-ECU

: CONNECTOR LOCK SWITCH 
  CONNECTOR CONNECTED: ON
  CONNECTOR DISCONNECTED: OFF

CONNECTOR
LOCK SWITCH

Driver's Air Bag Module (1st and 2nd Squib) Circuit

AC305233 AO

CONNECTOR: C-22

C-22 (Y)

AC305362

CONNECTOR: C-121

C-121 (Y)

AD

SRS-ECU

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-56

CAUTION

If DTC B1402 <1st squib> or B1482 <2nd squib> 
is set in the SRS-ECU, always diagnose the CAN 
main bus line.

.

CIRCUIT OPERATION

• The SRS-ECU judges how severe a collision is 

by detecting signals from the front impact sensors 
and the front air bag analog G-sensor. If the 
impact is over a predetermined level, the 
SRS-ECU sends an ignition signal. At this time, if 
the front air bag safing G-sensor is on, the SRS 
air bag will inflate. 

• The ignition signal is input to the air bag module 

via the clock spring to inflate the air bag.

.

DTC SET CONDITIONS
This DTC is set if there is abnormal resistance 
between the input terminals of the driver's air bag 
module (squib). However, if no DTC resets, the SRS 
warning light will be switched off (DTC will be 
retained). 

.

TROUBLESHOOTING HINTS

• Malfunction of the clock spring

• Damaged harness wires and connectors

• Short to the power supply in the driver's air bag 

module (squib) harness

• Malfunction of the SRS-ECU

.

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 resistor

• MB991866: Resister harness

AC305235AP

C-307 (Y)

CONNECTORS: C-305, C-307

CLOCK
SPRING

C-305 (Y)