Mitsubishi Evolution X. Manual - part 708

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-279

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-280

STEP 3. Check for any diagnostic trouble code.
Check the front impact sensor (LH).
(1) Disconnect the negative battery terminal.
(2) Alternate the front impact sensor (LH) and front impact 

sensor (RH), and then install the alternated sensors.

(3) Connect the negative battery terminal.
(4) Erase diagnostic trouble code from memory, and check the 

diagnostic trouble code.

Q: Is DTC U0171 set?

YES : Replace the front impact sensor (LH) with a new one 

(Refer to 

P.52B-380

). Go to Step 5.

NO :  Go to Step 4.

STEP 4. Check the harness wires for open circuit or short 
circuit between SRS-ECU connector C-37 (terminal No.21 
and 22) and front impact sensor (LH) connector A-46 
(terminal No.2 and 1).
NOTE: After inspecting intermediate connector A-42, C-131 
inspect the wiring harness. If the intermediate connector A-42, 
C-131 is damaged, repair or replace it.
Q: Are the harness wires between SRS-ECU connector 

C-37 (terminal No.21 and 22) and front impact sensor 
(LH) connector A-46 (terminal No.2 and 1) in good 
condition? 
YES : Go to Step 5.
NO :  Replace the harness wires between SRS-ECU 

connector C-37 and front impact sensor (LH) 
connector A-46.

STEP 5. 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 U0170 set?

YES : Replace SRS-ECU (Refer to 

P.52B-383

).

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-281

DTC U0171: Front Impact Sensor (RH) Communication Error

CAUTION

If DTC U0171 is set in the SRS-ECU, always diag-
nose the CAN main bus line.

.

FRONT IMPACT 
SENSOR (RH)

ACCELERO
METER

CPU

SRS-ECU

Front Impact Sensor (RH) Circuit

AC708949AD

Connector: A-42

A-42 (B)

AC708948

Connector: A-52

A-52 (Y)

AE

AC708951AC

C-37 (Y)

Connector: C-37

AC708950AG

C-131

Connector: C-131

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-282

CIRCUIT OPERATION

If an impact of set value or more is detected, the front 
impact sensor sends the coded acceleration data to 
SRS-ECU. Based on the acceleration data, 
SRS-ECU determines the necessity of driver's and 
front passenger's air bag deployment, and then turns 
ON the power supply circuit to the inflator.

.

DTC SET CONDITIONS

These DTCs are set if communication between the 
front impact sensor (RH) and the SRS-ECU is not 
possible or faulty.

.

TROUBLESHOOTING HINTS

• Damaged wiring harnesses or connectors

• Malfunction of the front impact sensor (RH)

• Malfunction of the SRS-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