Mitsubishi Galant 9G. Manual - part 1408

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-42

STEP 4. Check SRS-ECU connector C-121.
Q: Is the connector correctly engaged?

YES : Go to Step 5.
NO :  Engage the connector correctly. Then go to Step 10.

STEP 5. Check SRS-ECU connector C-121, clock spring 
connector C-307 and driver’s air bag module connector 
C-305. (Using scan tool MB991958, read the diagnostic 
trouble code.)
(1) Disconnect the negative battery terminal.
(2) Disconnect connectors C-121, C-307 and C-305, and then 

reconnect them.

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

diagnostic trouble code.

Q: Is DTC B1400 <1st squib> or B1480 <2nd squib> set?

YES : Go to Step 6.
NO :  The procedure is complete. It is assumed that DTC 

B1400 <1st squib> or B1480 <2nd squib> set 
because connector C-121, C-307 or C-305 was 
engaged improperly.

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

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

AC305235AO

C-307 (Y)

CONNECTORS: C-305, C-307

CLOCK
SPRING

11

12

13

14

C-307 HARNESS
SIDE CONNECTOR

C-305 (Y)

C-305 HARNESS
SIDE CONNECTOR

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-43

STEP 6. Check the driver's air bag module. (Using scan 
tool MB991958, read the diagnostic trouble code.)
(1) Disconnect the negative battery terminal.
(2) Slide the outer housing of the clock spring side of driver’s 

air bag module connector C-305 in the arrow direction 
shown, and disconnect the connector.

(3) Connect special tool MB991865 to special tool MB991866.

CAUTION

Do not insert a test probe into the terminal from its front 
side directly as the connector contact pressure may be 
weakened.
(4) Insert special tool MB991866 into clock spring side of 

driver’s air bag module connector C-305 (terminal No.1 and 
2 <1st squib> or No.3 and 4 <2nd squib>) by backprobing.

(5) Connect the negative battery terminal.
(6) Erase the diagnostic trouble code memory, and check the 

diagnostic trouble code.

Q:  Is DTC B1400 <1st squib> or B1480 <2nd squib> set?

YES : Go to Step 7.
NO :  Replace the driver's air bag module (Refer to 

P.52B-368

). Then go to Step 10. 

AC306561AC

OUTER HOUSING OF THE DRIVER'S 
AIR BAG MODULE CONNECTOR C-305

AC306758 AB

C-305 AIR BAG
MODULE
CONNECTOR

MB991865
(DUMMY RESISTOR : 3

Ω)

MB991866 (RESISTOR 
HARNESS)

(REAR VIEW

)

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-44

STEP 7. Check the clock spring. (Using scan tool 
MB991958, read the diagnostic trouble code.)
(1) Disconnect the negative battery terminal.
(2) Disconnect the clock spring connector C-307.

(3) Connect special tool MB991865 to special tool MB991866.

CAUTION

Do not insert a test probe into the terminal from its front 
side directly, as the connector contact pressure may be 
weakened.
(4) Insert special tool MB991866 into clock spring harness side 

connector C-307 (terminal No.36 and 37 <1st squib> or 
No.34 and 35 <2nd squib>) by backprobing.

(5) Connect the negative battery terminal.
(6) Erase the diagnostic trouble code memory, and check the 

diagnostic trouble code.

Q: Is DTC B1400 <1st squib> or B1480 <2nd squib> set?

YES : Go to Step 8.
NO :  Replace the clock spring (Refer to 

P.52B-368

). Then 

go to Step 10. 

AC305235AK

C-307 (Y)

CONNECTOR: C-307

C-307 HARNESS
SIDE CONNECTOR

CLOCK
SPRING

11

12

13

14

AC306767

C-307 CLOCK SPRING
CONNECTOR

AB

MB991865
(DUMMY RESISTOR : 3

Ω)

MB991866 (RESISTOR 
HARNESS)

1112

14

13

(REAR VIEW)

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-45

STEP 8. Check the driver’s air bag module circuit. Measure 
the resistance at SRS-ECU connector C-121.
(1) Disconnect SRS-ECU connector C-121.

DANGER

To prevent the air bag from deploying unintentionally, 
disconnect clock spring connector C-307 to short the 
squib circuit.

(2) Disconnect clock spring connector C-307.

CAUTION

Insert an insulator such as a cable tie to a depth of 4mm 
(0.16 inch) or more, otherwise the short spring will not be 
released.
(3) Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) 

thick] between terminals 36, 37 <1st squib> or 33, 34 <2nd 
squib> and the short spring to release the short spring.

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

AC308144

SECTION
A - A

C-121 HARNESS SIDE 
CONNECTOR
(FRONT VIEW)

CABLE TIE

SHORT SPRING

4 mm OR MORE

TERMINAL

A

AB

A

<1ST SQUIB>

AC308141

SECTION
A - A

C-121 HARNESS SIDE 
CONNECTOR
(FRONT VIEW)

CABLE TIE

SHORT SPRING

4 mm OR MORE

TERMINAL

AB

<2ND SQUIB>

A

A