Mitsubishi Evolution X. Manual - part 693

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-219

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)

• MB991865: Dummy resistor

• MB991884: Resister harness

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 "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 :  Go to Step 6.

AC608435

Data link connector

MB991827

MB991824

MB991910

AB

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-220

STEP 3. Check the driver's seat belt pre-tensioner.
(1) Disconnect the negative battery terminal.
(2) Disconnect driver's seat belt pre-tensioner connector D-25. 

Use a flat-tipped screwdriver to unlock the locking button at 
the harness side connector by withdrawing it toward you in 
two stages, and then disconnect the connector.

(3) Connect special tool MB991865 to special tool MB991884.
(4) Connect special tool MB991884 to the D-25 harness side 

connector.

(5) Connect the negative battery terminal.
(6) Erase diagnostic trouble code memory, and check the 

diagnostic trouble code.

Q: Is DTC B1C39 set?

YES : Go to Step 4.
NO :  Replace the driver's seat belt with pre-tensioner 

(Refer to 

P.52B-413

). Then go to Step 6.

AC608959

AC

Pre-tensioner

Harness side
connector

Locking 
button

Flat-tipped
screwdriver

AC301553CB

D-25 Harness side 
connector

MB991884 

(Resistor harness)

MB991865

(Dummy resistor: 3    )

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-221

STEP 4. Check the driver's seat belt pre-tensioner circuit. 
Measure the voltage at the SRS-ECU connector C-36.
(1) Disconnect the negative battery terminal.
(2) While pushing the part "A" indicated in the figure of the 

harness side connector, turn the lock lever to the direction 
of the arrow to release the lock lever, and disconnect the 
C-36 SRS-ECU connector.

DANGER

To prevent the seat belt pre-tensioner from deploying 
unintentionally, disconnect the driver’s seat belt 
pre-tensioner connector D-25 to short the squib cir-
cuit.

(3) Disconnect driver's seat belt pre-tensioner connector D-25. 

Use a flat-tipped screwdriver to unlock the locking button at 
the harness side connector by withdrawing it toward you in 
two stages, and then disconnect the connector.

CAUTION

Insert an insulator such as a cable tie to a depth of 4mm 
(0.16 inch) or more, otherwise the short spring will not be 
released.
(4) Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) 

thick] between terminals 45, 46 and the short spring to 
release the short spring.

(5) Connect the negative battery terminal.
(6) Ignition switch: "ON".

(7) Measure the voltage between C-36 harness side connector 

terminals 45, 46 and body ground.
Voltage should measure 0 volt.

Q: Is the measured voltage 0 volt?

YES : Erase the diagnostic trouble code memory, and check 

the diagnostic trouble code. If DTC B1C39 sets, 
replace the SRS-ECU (Refer to 

P.52B-383

). Then go 

to Step 6.

NO :  Go to Step 5.

AC507645

A

AC

Lock lever

AC608959

AC

Pre-tensioner

Harness side
connector

Locking 
button

Flat-tipped
screwdriver

AC507303 CC

A

A

C-36 Harness side
connector (front view)

Section
A - A

Cable tie

Short spring

4 mm (0.16 inch) or more

Terminal

AC608813

C-36 Harness side 
connector (front view)

BJ

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-222

STEP 5. Check the harness wires for short circuit to power 
supply between SRS-ECU connector C-36 (terminal No.45 
and 46) and driver's seat belt pre-tensioner connector D-25 
(terminal No.1 and 2).
Q: Are the harness wires between SRS-ECU connector 

C-36 (terminal No.45 and 46). and driver's seat belt 
pre-tensioner connector D-25 (terminal No.1 and 2) in 
good condition?
YES : Go to Step 6.
NO :  Replace the harness wires between SRS-ECU 

connector C-36 and driver's seat belt pre-tensioner 
connector D-25. Then go to Step 6.

STEP 6. 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 B1C39 set?

YES : Return to Step 1. 
NO :  The procedure is complete.

 DTC B1C3A: Driver's Pre-tensioner (Squib) System (Squib Circuit Open)

CONNECTOR
LOCK 
SWITCH

CONNECTOR
LOCK SWITCH

SEAT BELT
PRE-TENSIONER (LH)

SRS-ECU

Seat Belt Pre-Tensioner (LH) (Squib) Circuit