Mitsubishi Evolution X. Manual - part 654

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-63

DTC B1B03: Driver's Air Bag Module (1st squib) System (Short Circuit Between Squib Circuit 
Terminals)

 

DTC B1B07: Driver's Air Bag Module (2nd squib) System (Short Circuit Between Squib Circuit 
Terminals)

CAUTION

If DTC B1B03 <1st squib> or B1B07 <2nd squib> 
is set in the SRS-ECU, always diagnose the CAN 
bus lines.

.

SRS-ECU

CLOCK
SPRING

DRIVER'S AIR BAG
MODULE (SQUIB)

CONNECTOR LOCK SWITCH 

CONNECTOR COUPLED: ON 

CONNECTOR UNCOUPLED: OFF

NOTE

:   

 

 

Driver's Air Bag Module (Squib) Circuit

AC708951AC

C-37 (Y)

Connector: C-37

AC708953AB

Connectors: C-204, C-208

C-208 (Y)

C-204 (Y)

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

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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 SRS 
air bag will inflate. 

• The ignition signal is input to the air bag module 

via the clock spring to inflate the air bag.

.

DTC SET CONDITIONS

• This DTC is set if there is abnormal resistance 

between the input terminals of the driver's air bag 
module (squib). The most likely causes for this 
code to be set are the followings: 

• Short circuit in driver’s air bag module (squib) 

or harness

• Short circuit in the clock spring

.

TROUBLESHOOTING HINTS

• Improper engaged connector or defective short 

spring*

• Short circuit in the clock spring

• Short circuit between the driver's air bag module 

(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-37, 

C-204 or C-208 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

• MB991866: Resister harness

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-65

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 :  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

).

AC608435

Data link connector

MB991827

MB991824

MB991910

AB

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-66

STEP 3. Check SRS-ECU connector C-37, driver’s air bag 
module connector C-204 and clock spring connector 
C-208.
(1) Disconnect the negative battery terminal.
(2) Disconnect connectors C-37, C-204 and C-208, 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-37 SRS-ECU connector.

(4) Slide the outer housing of the clock spring side of driver’s 

air bag module connector C-204 in the arrow direction 
shown, and disconnect the connector.

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

diagnostic trouble code.

Q: Is DTC B1B03 <1st squib> or B1B07 <2nd squib> set?

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

B1B03 <1st squib> or B1B07 <2nd squib> set 
because connector C-37, C-204 or C-208 was 
engaged improperly.

AC506734

A

AD

Lock lever

AC605948

AC600868

AF

Outer housing of the driver's air bag 
module connector

Driver's air bag module 
Connector (4 pin yellow)

Horn connector

Lower column 
cover