Mitsubishi Galant 9G. Manual - part 1409

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-46

CAUTION

Do not insert a test probe into the terminal from its front 
side directly as the connector contact pressure may be 
weakened.
(4) Check for continuity between C-26 harness side connector 

terminals 36 and 37 <1st squib> or 33 and 34 <2nd squib>.
It should be open circuit.

Q: Does continuity exist? 

YES : Erase the diagnostic trouble code memory, and check 

the diagnostic trouble code. If DTC B1400 <1st 
squib> or B1481 <2nd squib> set, replace the 
SRS-ECU (Refer to 

P.52B-365

). Then go to Step 10.

NO :  Go to Step 9. 

STEP 9. Check the harness for short circuit between 
SRS-ECU connector C-121 (terminal No.36 and 37 <1st 
squib> or No.33 and 34 <2nd squib>) and clock spring 
connector C-307 (terminal No.13 and 14 <1st squib> or 
No.11 and 12 <2nd squib>).

AC301581

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-121 HARNESS SIDE 
CONNECTOR (REAR VIEW)

<1ST SQUIB>

AC

AC308145

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-121 HARNESS SIDE 
CONNECTOR (REAR VIEW)

<2ND SQUIB>

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

AC305235AK

C-307 (Y)

CONNECTOR: C-307

C-307 HARNESS
SIDE CONNECTOR

CLOCK
SPRING

11

12

13

14

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-47

NOTE: After inspecting intermediate connector C-22 inspect 
the wiring harness. If the intermediate connector C-22 is dam-
aged, repair or replace it.

Q: Are harness wires between SRS-ECU connector C-121 

(terminal No.36 and 37 <1st squib> or No.33 and 34 
<2nd squib>) and clock spring connector C-307 
(terminal No.13 and 14 <1st squib> or No.11 and 12 <2nd 
squib>) in good condition?
YES : Go to Step 10.
NO :  Replace the harness wires between SRS-ECU 

connector C-121 and clock spring connector C-307. 
Then go to Step 10.

STEP 10. 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 B1400 <1st squib> or B1480 <2nd squib> set?

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

AC305233

C-22 (Y)

CO

CONNECTOR: C-22

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-48

DTC B1401: Driver's Air Bag Module (1st Squib) System Fault 2 (Open in the Squib Circuit)
DTC B1481: Driver's Air Bag Module (2nd Squib) System Fault 2 (Open in the Squib Circuit)

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

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

CLOCK 
SPRING

AIR BAG DRIVE CIRCUIT

SRS-ECU

CONNECTOR
LOCK SWITCH

: CONNECTOR LOCK SWITCH
  CONNECTOR CONNECTED: ON
  CONNECTOR DICONNECTED: OFF

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-49

CAUTION

If DTC B1401 <1st squib> or B1481 <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 side air 
bag module (squib). The most likely causes for 
this code to be set are the followings: 

• Open circuit in the driver's air bag module 

(squib) or harness

• Open circuit in the clock spring

• Malfunction of connector contact

However, if no DTC reset, the SRS warning light will 
be switched off (DTC will be retained). 

.

TROUBLESHOOTING HINTS

• Open circuit in the clock spring

• Open circuit due to improper neutral position of 

the clock spring

• Open circuit in the driver's air bag module (squib) 

circuit

• Disengaged driver's air bag module (squib) con-

nector

• Improper connector contact

• 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)