Mitsubishi Evolution X. Manual - part 718

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-319

DTC B1B8E: Seat Slide Sensor (Power Supply Side) Short Circuit

CAUTION

If DTC B1B8E is set in the occupant classifica-
tion-ECU, always diagnose the CAN main bus 
lines.

.

CIRCUIT OPERATION

• The seat slide sensor sets the current value Hi or 

Low determined by the seat position.

• The occupant classification determines the seat 

position according to the current value from the 
seat slide sensor.

.

DTC SET CONDITIONS

This DTC is set if there is abnormal resistance 
between the input terminals of the seat slide sensor.

.

TROUBLESHOOTING HINTS

• Damaged wiring harnesses or connectors

• Short to the power supply in the seat slide sensor 

harness

• Malfunction of the seat slide sensor

• Malfunction of the occupant classification-ECU

OCCUPANT 
CLASSIFICATION-
ECU

HALL IC

SEAT SLIDE 
SENSOR (LH)

FRONT SEAT 
ASSEMBLY (RH)

Seat Slide Sensor Circuit

AC708954 AM

D-32 (GR)

Connectors: D-32, D-39, D-39-2

D-39, D-39-2

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-320

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)

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

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-321

STEP 3. Check the seat slide sensor circuit. Measure the 
voltage at the occupant classification-ECU connector 
D-39-2.
(1) Disconnect occupant classification connector-ECU 

connector D-39-2.

(2) Disconnect seat slide sensor connector D-32.
(3) Turn the ignition switch to the "ON" position.

CAUTION

Do not insert a test probe into the terminal from its front 
side directly, as the connector contact pressure may be 
weakened.
(4) Measure the voltage between D-39-2 harness side 

connector terminals 27, 29 and body ground.
Voltage should measure 0 volt.

Q: Is the measured voltage within the specified range?

YES : Erase the diagnostic trouble code memory, and check 

the diagnostic trouble code. If DTC B1B8E sets, 
replace the slide adjuster (LH) (Refer to GROUP 52A, 
Front Seat Assembly 

P.52A-24

).

NO :  Go to Step 4.

STEP 4. Check the harness wires for short circuit to power 
supply between the occupant classification-ECU 
connector D-39-2 (terminal No.27 and 29) and seat slide 
sensor connector D-32 (terminal No.2 and 1).
Q: Are the harness wires between occupant 

classification-ECU connector D-39-2 (terminal No.27 
and 29) and seat slide sensor connector D-32 (terminal 
No.2 and 1) in good condition?
YES : Go to Step 5.
NO :  Repair the harness wires between the occupant 

classification-ECU connector D-39-2 and seat slide 
sensor connector D-32. Then go to Step 5.

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 B1B8E set?

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

52A, Front seat assembly 

P.52A-24

).

NO :  The procedure is complete.

AC608813

D-39-2 Harness side 
connector (front view)

CC

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-322

DTC B1B91: Driver Seat Slide Sensor Configuration Mismatch

CAUTION

If DTC B1B91 is set in the occupant classifica-
tion-ECU, always diagnose the CAN main bus 
lines.

.

DTC SET CONDITIONS

These DTCs are set if there is an error in the coding 
data of the occupant classification-ECU.

.

TROUBLESHOOTING HINTS

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)

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

).

AC608435

Data link connector

MB991827

MB991824

MB991910

AB