Mitsubishi Evolution X. Manual - part 692

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-215

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 B1C38 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

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-216

STEP 4. Check the driver's seat belt pre-tensioner circuit. 
Measure the resistance 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.

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

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-217

(5) Check for continuity between C-36 harness side connector 

terminals 45, 46 and body ground.
It should be an open circuit.

Q: Is it open circuit?

YES : Erase the diagnostic trouble code memory, and check 

the diagnostic trouble code. If DTC B1C38 sets, 
replace the SRS-ECU (Refer to 

P.52B-383

). Then go 

to Step 6.

NO :  Go to Step 5.

STEP 5. Check harness wires for short circuit to ground 
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 B1C38 set?

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

AC608812

C-36 Harness side 
connector (front view)

GK

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-218

DTC B1C39: Driver's Pre-tensioner (Squib) System (Shorted to Squib Circuit Power Supply)

CAUTION

If DTC B1C39 is set in the SRS-ECU, always diag-
nose the CAN main bus line.

.

CIRCUIT OPERATION

The SRS-ECU judges how severe a collision is by 
detecting signals from the front impact sensors and 
the front air bag analog G-sensor. If the impact is 
over a predetermined level, the SRS-ECU sends an 
ignition signal. At this time, if the front air bag safing 
G-sensor is on, the pre-tensioner will deploy. 

.

DTC SET CONDITIONS

This DTC is set if there is abnormal resistance 
between the input terminals of the driver's seat belt 
pre-tensioner (squib).

.

TROUBLESHOOTING HITS

• Damaged wiring harnesses or connectors

• Short to the power supply in the driver's seat belt 

pre-tensioner (squib) harness

• Malfunction of the SRS-ECU

CONNECTOR
LOCK 
SWITCH

CONNECTOR
LOCK SWITCH

SEAT BELT
PRE-TENSIONER (LH)

SRS-ECU

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

AC708951AD

Connector: C-36

C-36 (Y)

AC708955AF

Connector: D-25

D-25 (B)