Mitsubishi Evolution X. Manual - part 715

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-307

STEP 3. Measure the resistance at occupant 
classification-ECU connector D-39-1.
(1) Disconnect the connector D-39-1.
(2) Check for continuity between D-39-1 harness side 

connector terminals 1, 3, 5, 7, 9 and body ground.
It should be open circuit.

Q: Is it open circuit? 

YES : Erase the diagnostic trouble code memory, and check 

the diagnostic trouble code. If DTC B1B79, B1B7E, 
B1B83, B1B88 sets. Replace the slide adjuster (RH) 
(Refer to GROUP 52A, Front Seat Assembly 

P.52A-24

).

NO :  Repair the wiring harness between occupant 

classification-ECU connector D-39-1 terminals 1, 3, 5, 
7, 9 and the body ground. Then go to Step 4.

STEP 4. 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 DTCs B1B79, B1B7E, B1B83, B1B88 set?

YES : Replace the slide adjuster (RH) (Refer to GROUP 

52A, Front Seat Assembly 

P.52A-24

).

NO :  There is an intermittent malfunction such as poor 

engaged connector(s) or open circuit (Refer to 
GROUP 00, How to Cope with Intermittent 
Malfunction 

P.00-15

).

AC608812 

D-39-1 Harness side 
connector (front view)

GQ

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-308

DTC B1B7A: Passenger Seat Weight Sensor (power supply side) Short-circuited or Open (front: LH)

 

DTC B1B7F: Passenger Seat Weight Sensor (power supply side) Short-circuited or Open (front: RH)

 

DTC B1B84: Passenger Seat Weight Sensor (power supply side) Short-circuited or Open (rear: LH)

 

DTC B1B89: Passenger Seat Weight Sensor (power supply side) Short-circuited or Open (rear: RH)

WEIGHT SENSOR 
(FRONT: LH)

WEIGHT SENSOR 
(REAR: LH)

WEIGHT SENSOR 
(REAR: RH)

WEIGHT SENSOR 
(FRONT: RH)

FRONT SEAT 
ASSEMBLY (RH)

OCCUPANT 
CLASSIFICATION-
ECU

Weight Sensor

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-309

CAUTION

If DTC B1B7A, B1B7F, B1B84 or B1B89 is set in 
the occupant classification-ECU, always diag-
nose the CAN main bus lines.

.

CIRCUIT OPERATION

The load data from the weight sensor is classified 
with the occupant classification-ECU, and its classi-
fied information is send to SRS-ECU by CAN bus 
line. The SRS-ECU determines the air bag deploy-
ment based on this classified information, and con-
trols the power supply circuit to the inflator. 

.

DTC SET CONDITIONS

• This DTC is set if the weight sensor wires are 

short-circuited to the power supply.

• This DTC is set if the weight sensor wire are open 

circuit

.

TROUBLESHOOTING HINTS

• Damaged wiring harnesses or connectors

• Short to the power supply in the weight sensor harness

• Open circuit in the weight sensor harness

• Malfunction of the weight sensor

• Malfunction of occupant classification-ECU

DIAGNOSIS

Required Special Tools:

•  MB991958: Scan Tool (M.U.T.-III Sub Assembly)

• MB991824: Vehicle Communication Interface (V.C.I.)

• MB991827: M.U.T.-III USB Cable

• MB991910: M.U.T.-III Main Harness A (Vehicles with 

CAN communication system)

AC708954 AK

Connectors: D-39-1, D-39-3, D-39-4, 
D-39-5, D-39-6

D-39-1, D-39-3, 
D-39-4, D-39-5, 
D-39-6

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-310

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-28

."

(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 

P.54C-14

).

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 : 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 Cope with Intermittent 
Malfunction 

P.00-15

).

AC608435

Data link connector

MB991827

MB991824

MB991910

AB