Mitsubishi Galant 9G. Manual - part 1473

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-302

DTC SET CONDITIONS

DTC is set when the resistance between input termi-
nals of the seat belt switch in the SRS-ECU is with-
out the standard value.
Cause of trouble in each DTC is as follows.

.

TROUBLESHOOTING HINTS

• Malfunction of the seat belt switch

• Damaged wiring harnesses or connectors 

• Malfunction of the SRS-ECU 

DIAGNOSIS

Required Special Tools:

• MB991222: Probe

• 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)

DTC

SYMPTOM

B1520

Malfunction of seat belt switch 

B1521

Malfunction of the Normal/Close terminal or short circuit in its harness

B1522

Short to body ground in the Normal/Close terminal harness

B1523

Short to the power supply in the Normal/Close terminal harness

B1524

Malfunction of the Normal/Open terminal or short circuit in its harness

B1525

Short to body ground in the Normal/Open terminal harness

B1526

Short to the power supply in the Normal/Open terminal harness

B1527

Malfunction of the COM terminal or short circuit in its harness

B1528

Short to body ground in the COM terminal harness

B1529

Short to the power supply in the COM terminal harness

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-303

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

CAUTION

To prevent damage to scan tool MB991958, always turn the 
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958. Refer to "How to connect the 

scan tool 

P.52B-30

."

(2) Connect scan tool MB991958 to the data link connector.
(3) Turn the ignition switch to the "ON" position.
(4) Diagnose the CAN bus line.
(5) Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the CAN bus line found to be normal?

YES : Go to Step 3.
NO :  Repair the CAN bus line (Refer to GROUP 54C, 

Diagnosis ). Then go to Step 2.

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 ).

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-304

STEP 3. Check the driver’s seat belt switch.

AC305264

AS

CONNECTOR: D-28

D-28 (B)

HARNESS SIDE

AC308221AB

D-28 DRIVER'S 
SEAT BELT SWITCH
CONNECTOR

BUCKLE

TONGUE

AC308214AB

D-28 DRIVER'S 
SEAT BELT SWITCH
CONNECTOR

AC308219AB

D-28 DRIVER'S 
SEAT BELT SWITCH
CONNECTOR

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-305

Disconnect driver’s seat belt switch connector D-28. Then 
check continuity between the switch terminals.

Q: Is driver’s seat belt switch in good condition?

YES : Go to Step 4.
NO :  Replace inner seat belt. (Refer to GROUP 52A, Front 

Seat Belt 

P.52A-32

.)

ITEM

TESTER 
CONNECTION

STANDARD 
VALUE

SPECIFIED 
CONDITION

Fastened seat 
belt

3 

− 5

820 

± 20 Ω

−

3 

− Ground

−

No continuity

5 

− Ground

−

No continuity

4 

− 5

−

Less than 2 
ohms

Unfastened 
seat belt

4 

− 5

820 

± 20 Ω

−

4 

− Ground

−

No continuity

5 

− Ground

−

No continuity

3 

− 5

−

Less than 2 
ohms

AC308215

D-28 DRIVER'S 
SEAT BELT SWITCH
CONNECTOR

AB

AC308218 AB

D-28 DRIVER'S 
SEAT BELT SWITCH
CONNECTOR