Mitsubishi Evolution X. Manual - part 686

 

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Mitsubishi Evolution X. Manual - part 686

 

 

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-191

DTC B1C2A: Side-air bag Module (LH) (Squib) System (Short Circuit between Squib Circuit Terminals)

CAUTION

If DTC B1C2A is set in the SRS-ECU, always diag-
nose the CAN bus lines.

.

CIRCUIT OPERATION

• The SRS-ECU judges how severe a collision is 

by detecting signals from the side impact sensor 
installed on the lower side of the center pillar. If 
the impact is over a predetermined level, the 
SRS-ECU sends an ignition signal. At this time, if 
the side collision safing G-sensor is on, the SRS 
air bag will inflate.

• The ignition signal is input to the side-air bag 

module to inflate the side-air bag.

.

DTC SET CONDITIONS

This DTC is set if there is abnormal resistance 
between the input terminals of the side-air bag mod-
ule (LH) (squib).

.

SIDE-AIR BAG MODULE
(SQUIB) (LH)

CONNECTOR
LOCK 
SWITCH

CONNECTOR
LOCK 
SWITCH

SRS-ECU

Side-airbag Module (Squib) (LH) Circuit

NOTE

: CONNECTOR COUPLED : ON

CONNECTOR UNCOUPLED : OFF

AC708951AD

Connector: C-36

C-36 (Y)

AC708954 AD

Connector: D-34

D-34 (Y)

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-192

TROUBLESHOOTING HINTS

• Improper engaged connector or defective short 

spring*

• Short circuit between the side-air bag module 

(LH) (squib) circuit terminals

• Damaged connector(s)

• Malfunction of the SRS-ECU

NOTE:  *: The squib circuit connectors integrate a 
"short" spring (which prevents the air bag from 
deploying unintentionally due to static electricity by 
shorting the positive wire to the ground wire in the 
squib circuit when the connectors are disconnected) 
(Refer to 

P.52B-3

). Therefore, if connector C-36 or 

D-34 is damaged or improperly engaged, the short 
spring may not be released when the connector 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

• MB991866: 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) Connect scan tool MB991958 to the data link connector.
(3) Turn the ignition switch to "ON" position.
(4) Diagnose the CAN bus line.
Q: Is the check result satisfactory?

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-193

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 side-air bag 
module (LH) connector D-34.
(1) Disconnect the negative battery terminal.
(2) Disconnect connectors D-34, and then reconnect them.
(3) 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.

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

diagnostic trouble code.

Q: Is DTC B1C2A out put?

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

B1C2A set because connector C-36 or D-34 was 
engaged improperly.

STEP 4. Check the side-air bag module (LH).
(1) Disconnect the negative battery terminal.
(2) Disconnect the side-air bag module (LH) connector D-34.
(3) Connect special tool MB991865 to special tool MB991866.

CAUTION

Do not insert a test probe into the terminal from its front 
side directly, as the connector contact pressure may be 
weakened.
(4) Insert special tool MB991866 into the D-34 harness side 

connector by backprobing.

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

diagnostic trouble code. 

Q: Is DTC B1C2A set?

YES : Go to Step 5.
NO :  Replace the front seatback (Refer to GROUP 52A, 

Front Seat Assembly 

P.52A-24

). Then go to Step 7.

AC507645

A

AC

Lock lever

AC507310 AW

D-34 

Side-airbag 

module (LH) connector

D-34 
Harness side 
connector

MB991865
(Dummy resistor: 3    )

MB991866 

(Resistor harness)

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-194

STEP 5. Check the side-air bag module (LH) 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 air bag from deploying unintentionally, 
disconnect the side-air bag module (LH) connector 
D-34 to short the squib circuit.

(3) Disconnect side-air bag module (LH) connector D-34.

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 31, 32 and the short spring to 
release the short spring.

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

terminals 31 and 32.
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 B1C2A sets, 
replace the SRS-ECU (Refer to 

P.52B-383

). Then go 

to Step 7

NO :  Go to Step 6. 

AC507645

A

AC

Lock lever

AC507303 CA

A

A

C-36 Harness side
connector (front view)

Section
A - A

Cable tie

Short spring

4 mm (0.16 inch) or more

Terminal

AC608812

C-36 Harness side 
connector (front view)

GE

 

 

 

 

 

 

 

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