Mitsubishi Evolution X. Manual - part 695

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-227

(5) Connect D-25 harness side connector to special tool 

MB991884.

(6) Check for continuity between the following terminals. It 

should be less than 2 ohms.

• SRS-ECU connector C-36 (terminal No.45) and the spe-

cial tool (terminal No.2)

• SRS-ECU connector C-36 (terminal No.46) and the spe-

cial tool (terminal No.1)

Q: Does continuity exist?

YES : Erase the diagnostic trouble code memory, and 

recheck if any DTC set. If DTC B1C3A set, replace 
the SRS-ECU (Refer to 

P.52B-383

). Then go to Step 

5.

NO :  Replace harness wires between SRS-ECU connector 

C-36 and driver’s seat belt pre-tensioner connector 
D-25. Then go to Step 5.

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 B1C3A set?

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

AC201287EL

D-25 Harness side 
connector

MB991884 
(Resistor harness)

AC608812GL

C-36 Harness side 
connector (front view)

Resistor harness 
side connector

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-228

DTC B1C3B: Driver's Pre-tensioner (Squib) System (Short Circuit Between Squib Circuit Terminals)

CAUTION

If DTC B1C3B 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 side seat 
belt pre-tensioner (squib).

.

TROUBLESHOOTING HITS

• Improper engaged connector or defective short 

spring*

• Short circuit between the driver's seat belt 

pre-tensioner (squib) circuit terminals

• Damaged connector(s)

• 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)

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-229

NOTE: *: The squib circuit connectors integrate a 
"short" spring (which prevents the seat belt pre-ten-
sioner from deploying unintentionally due to static 
electricity by shorting the positive wire to the ground 
wire in the squib circuit when the connectors are dis-
connected) (Refer to 

P.52B-3

). Therefore, if connec-

tor C-36 or D-25 is damaged or improperly engaged, 
the short spring may not be released when the con-
nector is connected.

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

).

AC608435

Data link connector

MB991827

MB991824

MB991910

AB

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-230

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 :  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 SRS-ECU connector C-36 and driver’s seat 
belt pre-tensioner connector D-25.
(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. Then connect the connector.

(3) After disconnecting the D-25 harness side connectors, 

connect the connectors again. For the D-25 connector 
disconnection, 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.

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

diagnostic trouble code.

Q: Is DTC B1C3B set?

YES : Go to Step 4.
NO :  The procedure is complete. It is assumed that DTC 

B1C3B set because connector C-36 or D-25 was 
engaged improperly.

AC507645

A

AC

Lock lever

AC608959

AC

Pre-tensioner

Harness side
connector

Locking 
button

Flat-tipped
screwdriver