Mitsubishi 380. Manual - part 780

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-44

STEP 1. Using diagnostic tool MB991958, diagnose the 
CAN bus line.

CAUTION

To prevent damage to diagnostic tool MB991958, always 
turn the ignition switch to the "LOCK" (OFF) position 
before connecting or disconnecting diagnostic tool 
MB991958.
(1) Connect diagnostic tool MB991958. Refer to "How to 

connect the diagnostic tool 

P.52B-19

."

(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 ).

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

00DB076A

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-45

STEP 3. Check the driver's air bag module. (Using 
diagnostic tool MB991958, read the diagnostic trouble 
code.)
(1) Disconnect the negative battery terminal.
(2) Slide the outer housing of the 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 air bag 

module connector C-305 (terminal No.1 and 2 ) by 
testprobe.

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

diagnostic trouble code.

Q:  Is DTC B1403  set?

YES : Go to Step 4.
NO :  Replace the driver's air bag module (Refer to 

P.52B-237

). Then go to Step 7. 

AC306561AC

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

AC306758 AB

C-305 AIR BAG
MODULE
CONNECTOR

MB991865
(DUMMY RESISTOR : 3Ω)

MB991866 (RESISTOR 
HARNESS)

(REAR VIEW)

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-46

STEP 4. Check the clock spring. (Using diagnostic 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.13 and 14 ) by testprobe.

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

diagnostic trouble code.

Q: Is DTC B1403  set?

YES : Go to Step 5.
NO :  Replace the clock spring (Refer to 

P.52B-237

). Then 

go to Step 7. 

52DB008A

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 : 3Ω)

MB991866 (RESISTOR 

HARNESS)

1112 14

13

(REAR VIEW)

SRS AIR BAG DIAGNOSIS

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-47

STEP 5. Check the driver’s air bag module circuit. Measure 
the resistance at the SRS-ECU connector C-121.
(1) Disconnect SRS-ECU connector C-121.

DANGER

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

(2) Disconnect the 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.
(3) Check for continuity between C-121 harness side connector 

terminals 28 and 27  and body ground.
It should be open circuit.

Q: Does continuity exist?

YES : Erase the diagnostic trouble code memory, and check 

the diagnostic trouble code. If DTC B1403  sets, 
replace the SRS-ECU (Refer to 

P.52B-234

). Then go 

to Step 6. 

NO :  Go to Step 7.

24DB062A

CONNECTOR: C-121

C-121 (Y)

SRS-ECU

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

INSTRUMENT

HARNESS

CONNECTOR

(REAR VIEW)

52DB008A

C-307 (Y)

CONNECTOR: C-307

C-307 HARNESS

SIDE CONNECTOR

CLOCK

SPRING

11

12

13

14