Mitsubishi Evolution X. Manual - part 714

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-303

STEP 4. Check the wiring harness between occupant 
classification-ECU connector D-39-1 (terminal 1) and 
weight sensors D-39-3, D-39-4, D-39-5, and D-39-6 (terminal 
2).
Q: Is the wiring harness between occupant 

classification-ECU connector D-39-1 (terminal 1) and 
weight sensor D-39-3, D-39-4, D-39-5, D-39-6 (terminal 2) 
in good condition?
YES : Go to Step 5.
NO :  The wiring harness may be damaged or the 

connector(s) may have loose, corroded or damaged 
terminals, or terminals pushed back in the connector. 
Repair the wiring harness as necessary.

STEP 5. Recheck for diagnostic trouble code.
Check again if the DTC is set to the occupant classifica-
tion-ECU.
(1) Erase the DTC.
(2) Turn the ignition switch from "LOCK" (OFF) position to "ON" 

position.

(3) Check if DTC is set.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the DTC 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

).

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-304

DTC B1B79: Passenger Seat Weight Sensor (ground side) Short-circuited (front: LH)

 

DTC B1B7E: Passenger Seat Weight Sensor (ground side) Short-circuited (front: RH)

 

DTC B1B83: Passenger Seat Weight Sensor (ground side) Short-circuited (rear: LH)

 

DTC B1B88: Passenger Seat Weight Sensor (ground side) Short-circuited (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-305

CAUTION

If DTC B1B79, B1B7E, B1B83 or B1B88 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 wire is short-cir-
cuited to ground.

.

TROUBLESHOOTING HINTS

• Disengaged wire harnesses or connector

• Short to the ground in the weight sensor harness

• Malfunction of the weight sensor

• Malfunction of the 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 AL

Connector: D-39-1

D-39-1

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-306

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 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 Cope with Intermittent 
Malfunction 

P.00-15

).

AC608435

Data link connector

MB991827

MB991824

MB991910

AB