Mitsubishi Galant 9G. Manual - part 1482

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-338

.

CIRCUIT OPERATION

• The SRS-ECU is energized by the ignition switch 

(IG1) through multi-purpose fuse 22 and the 
SRS-ECU terminal 23 and multi-purpose fuse 23 
and the SRS-ECU terminal 24.

• If the power supply to the SRS-ECU has failed, 

scan tool (MUT-III Sub Assembly) will not be able 
to communicate with it.

.

TROUBLESHOOTING HINTS (THE MOST 
LIKELY CAUSES FOR THIS CASE:) 

• Damaged wiring harness or connector

• Defective battery

• Charging system failed

• 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)

.

AC305415

CONNECTORS : C-211, C-215

C-211

C-215

AZ

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-339

STEP 1. Measure the resistance at SRS-ECU connector 
C-121.
(1) Disconnect the connector C-121.

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 C-121 harness side connector 

terminals 40 and body ground.
It should be 2 ohms or less.

Q: Is the measured resistance 2 ohms or less?

YES : Then go to Step 2.
NO :  Repair the wiring harness between SRS-ECU 

connector C-121 terminals 40 and the body ground. 
Then go to Step 5.

STEP 2. Check the harness wires for short circuit to 
ground between SRS-ECU connector C-121 (terminal 
No.23 and 24) and ignition switch connector C-308 
(terminal No.2).

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

AC308208

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)

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

AC305235AG

CONNECTOR: C-308

C-308

2
5

4

1

6

3

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-340

NOTE: After inspecting intermediate connectors C-22, C-211 
and C-215 inspect the wiring harness. If intermediate connec-
tors C-22, C-211 and C-215 are damaged, repair or replace 
them. Refer to GROUP 00E, Harness Connector Inspection . 
Then go to Step 5.

Q: Are the harness wires between SRS-ECU connector 

C-121 (terminal No.23 and 24) and ignition switch 
connector C-308 (terminal No.2) in good condition?
YES : Go to Step 3.
NO :  Replace the harness wires between SRS-ECU 

connector C-121 and ignition switch connector C-308. 
Then go to Step 5.

STEP 3. Check the battery.
Check the battery (Refer to GROUP 54A, Battery test ).

Q: Is the battery in good condition?

YES : Go to Step 4.
NO :  Charge or replace the battery. Then go to Step 5.

STEP 4. Check the charging system.
Check the charging system (Refer to GROUP 16, Charging 
system diagnosis ).

Q: Is the charging system in good condition?

YES : Go to Step 5.
NO :  Repair or replace the charging system 

component(s).Then go to Step 5.

AC305233 AI

CONNECTOR: C-22

C-22 (Y)

AC305416

CONNECTORS: C-211, C-215

JUNCTION BLOCK 
(FRONT VIEW)

C-215

C-211

HARNESS SIDE

C-211

HARNESS SIDE

C-215

AK

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-341

STEP 5. Retest the system.

Q: Can the SRS-ECU communicate with the scan tool 

(MUT-III Sub Assembly)?
YES : It can be assumed that this malfunction is intermittent. 

Refer to GROUP 00, How to Use 
Troubleshooting/Inspection Service Points 

− How to 

Cope with Intermittent Malfunctions .

NO :  Replace the SRS-ECU (Refer to 

P.52B-365

). Then go 

to Step 6.

STEP 6. Retest the system.

Q: Can the SRS-ECU communicate with the scan tool 

(MUT-III Sub Assembly)?
YES : The procedure is complete.
NO :  Go to Step 1.