Mitsubishi Galant 9G. Manual - part 1451

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-214

STEP 4. Check the SRS-ECU connector C-122.
Q: Is the connector correctly engaged?

YES : Go to Step 5.
NO :  Engage the connector correctly. Then go to Step 9.

STEP 5. Check SRS-ECU connector C-122 and driver’s 
seat belt pre-tensioner connector D-21. (Using scan tool 
MB991958, read the diagnostic trouble code.)
(1) Disconnect the negative battery terminal.
(2) Disconnect connectors C-122 and D-21, and then 

reconnect them. For connector D-21, use a flat-tipped 
screwdriver to unlock the locking button at the harness side 
connector by withdrawing it toward you in two stages, and 
then disconnect the connector.

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

diagnostic trouble code.

Q: Is DTC B1470 set?

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

B1470 set because connector C-122 or D-21 was 
engaged improperly.

AC305362

CONNECTOR: C-122

C-122 (Y)

AI

SRS-ECU

C-122 
Harness side
connector 
(rear view)

A

B

18

10

15

7

13

5

14

6

16

8

17

9

19

11

20

12

1 2

3 4

AC305362

CONNECTOR: C-122

C-122 (Y)

AI

SRS-ECU

C-122 
Harness side
connector 
(rear view)

A

B

18

10

15

7

13

5

14

6

16

8

17

9

19

11

20

12

1 2

3 4

AC306920AC

CONNECTOR: D-21

D-21 (B)

FOWARD

CENTER
PILLAR

HARNESS SIDE
CONNECTOR
(FRONT VIEW)

2 1

AC103556 AT

LOCKING BUTTON

FLAT-TIP SCREW
DRIVER

D-21 HARNESS 
SIDE CONNECTOR

D-21 DRIVER'S 
SEAT BELT
PRE-TENSIONER
CONNECTOR

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-215

STEP 6. Check the driver's seat belt pre-tensioner. (Using 
scan tool MB991958, read the diagnostic trouble code.)
(1) Disconnect the negative battery terminal.
(2) Disconnect driver's seat belt pre-tensioner connector D-21. 

Use a flat-tipped screwdriver to unlock the locking button at 
the harness side connector by withdrawing it toward you in 
two stages, and then disconnect the connector.

(3) Connect special tool MB991865 to special tool MB991884.
(4) Connect special tool MB991884 to the D-21 harness side 

connector.

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

diagnostic trouble code.

Q: Is DTC B1470 set?

YES : Go to Step 7.
NO :  Replace the driver's seat belt pre-tensioner (Refer to 

P.52B-380

). Then go to Step 9.

AC306920AC

CONNECTOR: D-21

D-21 (B)

FOWARD

CENTER
PILLAR

HARNESS SIDE
CONNECTOR
(FRONT VIEW)

2 1

AC103556 AT

LOCKING BUTTON

FLAT-TIP SCREW
DRIVER

D-21 HARNESS 
SIDE CONNECTOR

D-21 DRIVER'S 
SEAT BELT
PRE-TENSIONER
CONNECTOR

MB991884
MB991885

AC103283AO

MB991865
(DUMMY RESISTOR : 3

Ω

)

MB991884
(RESISTOR 
HARNESS)

D-21  HARNESS SIDE 
CONNECTOR

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-216

STEP 7. Check the driver’s seat belt pre-tensioner circuit. 
Measure the resistance at the SRS-ECU connector C-122.
(1) Disconnect SRS-ECU connector C-122.

DANGER

To prevent the seat belt pre-tensioner from deploying 
unintentionally, disconnect the driver’s seat belt 
pre-tensioner connector D-21 to short the squib cir-
cuit.

(2) Disconnect driver's seat belt pre-tensioner connector D-21. 

Use a flat-tipped screwdriver to unlock the locking button at 
the harness side connector by withdrawing it toward you in 
two stages, and then disconnect the connector.

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 7, 8 and the short spring to release 
the short spring.

AC305362

CONNECTOR: C-122

C-122 (Y)

AI

SRS-ECU

C-122 
Harness side
connector 
(rear view)

A

B

18

10

15

7

13

5

14

6

16

8

17

9

19

11

20

12

1 2

3 4

AC306920AC

CONNECTOR: D-21

D-21 (B)

FOWARD

CENTER
PILLAR

HARNESS SIDE
CONNECTOR
(FRONT VIEW)

2 1

AC103556 AT

LOCKING BUTTON

FLAT-TIP SCREW
DRIVER

D-21 HARNESS 
SIDE CONNECTOR

D-21 DRIVER'S 
SEAT BELT
PRE-TENSIONER
CONNECTOR

AC308180 AB

A

A

C-122 HARNESS SIDE
CONNECTOR (FRONT VIEW)

TERMINAL

CABLE TIE

SHORT SPRING

4 mm (0.16 inch) OR MORE

SEC-
TION
A - A

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-217

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-122 harness side connector 

terminals 7 and 8.
It should be open circuit.

Q: Does continuity exist?

YES : Go to Step 8.
NO :  Erase the diagnostic trouble code memory, and check 

the diagnostic trouble code. If DTC B1470 sets, 
replace the SRS-ECU (Refer to 

P.52B-365

). Then go 

to Step 9.

STEP 8. Check the harness for short circuit between 
SRS-ECU connector C-122 (terminal No.7 and 8) and 
driver’s seat belt pre-tensioner connector D-21 (terminal 
No.1 and 2).
Q: Are harness wires between SRS-ECU connector C-122 

(terminal No.29 and 30) and driver’s seat belt 
pre-tensioner connector D-21 (terminal No.1 and 2) in 
good condition?
YES : Go to Step 9.
NO :  Replace the harness wires between SRS-ECU 

connector C-122 and driver’s seat belt pre-tensioner 
connector D-21. Then go to Step 9.

AC308179

A

B

18

10

15

7

13

5

14

6

16

8

17

9

19

11

20

12

1 2

3 4

C-122 CONNECTOR
HARNESS SIDE
(REAR VIEW)

AB

AC305362

CONNECTOR: C-122

C-122 (Y)

AI

SRS-ECU

C-122 
Harness side
connector 
(rear view)

A

B

18

10

15

7

13

5

14

6

16

8

17

9

19

11

20

12

1 2

3 4

AC306920AC

CONNECTOR: D-21

D-21 (B)

FOWARD

CENTER
PILLAR

HARNESS SIDE
CONNECTOR
(FRONT VIEW)

2 1