Mitsubishi Evolution X. Manual - part 709

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-283

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

).

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

sensor (LH), 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 U0170 set?

YES : Replace the front impact sensor (RH) 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.23 
and 24) and front impact sensor (RH) connector A-52 
(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.23 and 24) and front impact sensor 
(RH) connector A-52 (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 (RH) 
connector A-52.

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-284

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 U0171 set?

YES : Replace the 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

).

DTC U0172: Side Impact Sensor (LH) Communication Error

SIDE IMPACT 
SENSOR
(LH)

SRS-ECU

ACCELERO
METER

CPU

Side Impact Sensor (LH) Circuit

AC708951AD

Connector: C-36

C-36 (Y)

AC708955AJ

Connector: D-26

D-26 (Y)

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-285

CAUTION

If DTC U0172 is set in the SRS-ECU, always diag-
nose the CAN main bus line.

.

CIRCUIT OPERATION

If an impact of set value or more is detected, the side 
impact sensor sends the coded acceleration data to 
SRS-ECU. Based on the acceleration data, 
SRS-ECU determines the necessity of side-air bag 
and curtain 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 
side impact sensor (LH) and the SRS-ECU is not 
possible or faulty.

.

TROUBLESHOOTING HINTS

• Damaged wiring harnesses or connectors

• Malfunction of the side impact sensor (LH)

• 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

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-286

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

).

STEP 3. Check for any diagnostic trouble code.
Check the side impact sensor (LH).
(1) Disconnect the negative battery terminal.
(2) Alternate the side impact sensor (LH) and side 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 U0175 set?

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

(Refer to 

P.52B-402

). 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-36 (terminal No.49 
and 50) and side impact sensor (LH) connector D-26 
(terminal No.1 and 2).
Q: Are the harness wires between SRS-ECU connector 

C-36 (terminal No.49 and 50) and side impact sensor 
(LH) connector D-26 (terminal No.1 and 2) in good 
condition? 
YES : Go to Step 5.
NO :  Replace the harness wires between SRS-ECU 

connector C-36 and side impact sensor (LH) 
connector D-26.

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 U0172 set?

YES : Replace the 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

).