Mitsubishi Galant 9G. Manual - part 1477

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-318

STEP 5. Check the harness wires between SRS-ECU 
connector C-120 (terminal No.52, 65 and 51) and 
passenger’s seat belt switch connector D-29 (terminal 
No.1, 2 and 3).
Q: Are harness wires between SRS-ECU connector C-120 

(terminal No.52, 65 and 51) and passenger’s seat belt 
switch connector D-29 (terminal No.1, 2 and 3) in good 
condition?
YES : Go to Step 6.
NO :  Replace the harness wires between SRS-ECU 

connector C-120 and passenger’s seat belt switch 
connector D-29. Then go to Step 6.

STEP 6. 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 B1530, B1531, B1532, B1533, B1534, B1535, 

B1536, B1537, B1538 or B1539 set?
YES : Return to Step 1. 
NO :  The procedure is complete.

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)

AC305264

AT

CONNECTOR: D-29

HARNESS SIDE

AC305412

AB

MB991910

DATA LINK

CONNECTOR

MB991824

MB991827

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-319

DTC B1540: Occupant classification-ECU malfunction DTC B1541: Occupant classification-ECU 
calibration malfunction DTC B1542: Occupant classification sensor (S1) malfunction DTC B1543: 
Occupant classification sensor (S2) malfunction DTC B1558: Occupant classification-ECU ID-cord 
malfunction 

CAUTION

If DTCs are set in the occupant classifica-
tion-ECU, always diagnose the CAN main bus 
line.

DTC SET CONDITIONS

• These DTC are set when a fault is detected in the 

occupant classification-ECU. The most likely 
causes for this code to be set are shown in the 
table below:

TROUBLESHOOTING HINTS

• Malfunction of the occupant classification-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)

CODE NO.

PART/CIRCUIT INTEGRAL TO 
occupant classification-ECU

SYMPTOM

B1540

Occupant classification-ECU

• Malfunction of occupant classification-ECU

B1541

• Malfunction of calibration function 

B1542

Occupant classification-sensor

• Malfunction of occupant classification sensor (S1)

B1543

• Malfunction of occupant classification sensor (S2)

B1558

Occupant classification-ECU

• Malfunction of ID code in occupant classification-ECU

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-320

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) 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 DTCs set?

YES : Replace the front seat slide adjuster (Refer to 

GROUP 52A, front seat assembly 

P.52A-25

).

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-321

DTC B1545: Occupant classification-ECU for Power Supply Circuit
DTC B1546: Occupant classification-ECU for Communication System

Occupant Classification Sensor Circuit

OCCUPANT
CLASSIFICATION
DETECTION
CIRCUIT

OCCUPANT
CLASSIFICATION
SENSOR (LH)

SRS-ECU

IGNITION
SWITCH (IG1)

JUNCTION
BLOCK

OCCUPANT
CLASSIFICATION-ECU

OCCUPANT
CLASSIFICATION
SENSOR (RH)

AC305233 AO

CONNECTOR: C-22

C-22 (Y)

AC305362

CONNECTOR: C-120

C-120 (Y)

AC

SRS-ECU