Mitsubishi Galant 9G. Manual - part 1430

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-130

STEP 2. Recheck for diagnostic trouble code.
Check again if the DTC is set.
(1) Erase the DTC.
(2) Turn the ignition switch to "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 ).

STEP 3. Check the side-airbag module (RH). (Using scan 
tool MB991958, read the diagnostic trouble code.)
(1) Disconnect the negative battery terminal.
(2) Disconnect the side-airbag module (RH) connector D-32.

(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 the D-32 harness side 

connector by backprobing.

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

diagnostic trouble code. 

Q: Is DTC B1421 set?

YES : Go to Step 4.
NO :  Replace the seatback frame of the front seat (RH) 

(Refer to GROUP 52A, Front Seat 

P.52A-25

). Then 

go to Step 5.

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AC307779

D-32 (R)

AD

2

1

HARNESS SIDE
CONNECTOR
(REAR VIEW)

CONNECTOR : D-32

AC006042BO

MB991866
(RESISTOR HARNESS)

D-32 HARNESS SIDE
CONNECTOR

D-32 SIDE-AIRBAG 
MODULE (RH) CONNECTOR

MB991865 (DUMMY 
RESISTOR: 3

 

Ω

)

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-131

STEP 4. Check the harness for open circuit between 
SRS-ECU connector C-120 (terminal No.57 and 58) and the 
side-airbag module (RH) connector D-32 (terminal No.1 
and 2).
(1) Disconnect SRS-ECU connector C-120 and side-airbag 

module (RH) connector D-32.

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 the following terminals. It 

should be less than 2 ohms.

• SRS-ECU connector C-120 (terminal No.57) and the 

side-airbag module (RH) connector D-32 (terminal No.2)

• SRS-ECU connector C-120 (terminal No.58) and the 

side-airbag module (RH) connector D-32 (terminal No.1)

Q: Does continuity exist?

YES : Erase the diagnostic trouble code memory, and check 

the diagnostic trouble code. If DTC B1421 sets, 
replace the SRS-ECU (Refer to 

P.52B-365

). Then go 

to Step 5.

NO :  Replace the harness wires between SRS-ECU 

connector C-120 and side-airbag module (RH) 
connector D-32. Then go to Step 5.

AC305362

CONNECTOR: C-120

C-120 (Y)

AG

SRS-ECU

63

55

51

69

61

66

58

65

64

56 57

68

60

67

59

70

62

53

52 B

A

54

C-120 
Harness side
connector 
(rear view)

AC307779

D-32 (R)

AD

2

1

HARNESS SIDE
CONNECTOR
(REAR VIEW)

CONNECTOR : D-32

AC301580

1 2

63

55

51

69

61

66

58

65

64

56 57

68

60

67

59

70

62

53

52 B

A

54

C-120 
HARNESS SIDE
CONNECTOR
(REAR VIEW)

D-32 
HARNESS SIDE
CONNECTOR 
(REAR VIEW)

AC

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-132

STEP 5. 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 B1421 set?

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

DTC B1422: Side-Airbag Module (RH) (Squib) System Fault Power Supply Circuit (Short-Circuited to 
Power Supply)

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

SIDE AIR BAG
MODULE
(SQUIB) (RH)

AIR BAG DRIVE CIRCUIT

SRS-ECU

CONNECTOR
LOCK SWITCH

CONNECTOR
LOCK SWITCH

Side-Airbag Module (RH) (Squib) Circuit

NOTE
  : CONNECTOR
    CONNECTED
    : ON
    CONNECTOR
    DISCONNECTED
    : OFF

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-133

CAUTION

If DTC B1422 is set in the combination meter, 
always diagnose the CAN bus lines.

.

CIRCUIT OPERATION

• The SRS-ECU judges how severe a collision is 

by detecting signals from the left and right side 
impact sensors. If the impact is over a predeter-
mined level, the SRS-ECU sends an ignition sig-
nal. At this time, if the side-airbag safing 
G-sensor is on, the SRS side-airbag will inflate.

• The ignition signal is input to the side-airbag 

module to inflate the side-airbag.

.

DTC SET CONDITIONS

This DTC is set if there is abnormal resistance 
between the input terminals of the side-airbag mod-
ule (RH) (squib).

.

TROUBLESHOOTING HINTS

• Damaged wiring harnesses or connectors

• Short to the power supply in the side-airbag mod-

ule (RH) (squib) harness

• 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

AC305362

CONNECTOR: C-120

C-120 (Y)

AC

SRS-ECU

AC307779

D-32 (R)

AC

CONNECTOR : D-32