Mitsubishi Galant 9G. Manual - part 1478

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-322

CAUTION

If DTC B1545 or B1546 is set in the SRS-ECU, 
always diagnose the CAN main bus line.

.

CIRCUIT OPERATION

The load data from the occupant classification sen-
sor is classified with the occupant classification-ECU, 
and its classified information is send to SRS-ECU. 
The SRS-ECU determines the air bag deployment 
based on this classified information, and controls the 
power supply circuit to the inflator. 

.

DTC SET CONDITIONS

These DTCs are set if communication between the 
occupant classification-ECU and the SRS-ECU is not 
possible or communication is faulty.

.

TROUBLESHOOTING HINTS

• Damaged wiring harnesses or connectors

• Malfunction of the occupant classification-ECU

• 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

AC308166

CONNECTOR : D-30

AB

D-30 (GR)

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-323

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 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

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-324

STEP 3. Measure the resistance at occupant 
classification-ECU connector D-30.
(1) Disconnect the connector D-30.

(2) Check for continuity between D-30 harness side connector 

terminals 1 and body ground.
It should be 2 ohms or less.

Q: Is the measured resistance 2 ohms or less?

YES : Then go to Step 4.
NO :  Repair the wiring harness between occupant 

classification-ECU connector D-30 terminals 1 and 
the body ground. Then go to Step 8.

STEP 4. Measure the voltage at occupant 
classification-ECU connector D-30.
(1) Disconnect the connector D-30.
(2) Turn the ignition switch to the "ON" position.

(3) Measure the voltage between terminal 2 and ground. It 

should measure approximately 12 volts (battery positive 
voltage).

Q: Is battery positive voltage (approximately 12 volts) 

present?
YES : Go to Step 5.
NO :  Go to Step 8.

AC308166

CONNECTOR : D-30

AC

D-30 (GR)

HARNESS SIDE

AC308191AB

D-30 HARNESS SIDE
CONNECTOR

AC308166

CONNECTOR : D-30

AC

D-30 (GR)

HARNESS SIDE

AC308192AB

D-30 HARNESS SIDE
CONNECTOR

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-325

STEP 5. Check the harness wires for open circuit or short 
circuit between occcupant classification-ECU connector 
D-30 (terminal No.2) and ignition switch connector C-308 
(terminal No.2).

AC308166

CONNECTOR : D-30

AC

D-30 (GR)

HARNESS SIDE

AC305235AG

CONNECTOR: C-308

C-308

2
5

4

1

6

3