Mitsubishi Evolution X. Manual - part 659

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-83

DTC B1B0A: Passenger's (Front) Air Bag Module (1st squib) System (Squib Circuit Open)

 

DTC B1B0E: Passenger's (Front) Air Bag Module (2nd squib) System (Squib Circuit Open)

CAUTION

If DTC B1B0A <1st squib> or B1B0E <2nd squib> 
is set in the SRS-ECU, always diagnose 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 SRS 
air bag will inflate. 

• The ignition signal is input to the air bag module 

to inflate the air bag.

.

DTC SET CONDITIONS

This DTC is set if there is abnormal resistance 
between the input terminals of the passenger’s 
(front) air bag module (squib).

.

TROUBLESHOOTING HINTS

• Open circuit in the passenger's (front) air bag 

module (squib) circuit

• Improper connector contact

• Malfunction of the SRS-ECU

PASSENGER'S (FRONT) 
AIR BAG MODULE
(SQUIB)

SRS-ECU

CONNECTOR LOCK SWITCH 

CONNECTOR COUPLED: ON 

CONNECTOR UNCOUPLED: OFF

NOTE

:   

 

 

Passenger's (Front) Air Bag Module (Squib) Circuit

AC708951AE

C-37 (Y)

C-14 (Y)

Connectors: C-14, C-37

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-84

DIAGNOSIS

Required Special Tools:

• MB991958: Scan Tool (M.U.T.-III Sub Assembly)

• MB991824: Vehicle Communication Interface (V.C.I.)

• MB991817: M.U.T.-III USB Cable

• MB991910: M.U.T.-III Main Harness A (Vehicles with 

CAN Communication System)

• MB991865: Dummy resister

• 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) 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 the "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

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-85

STEP 3. Check the passenger's (front) air bag module.
(1) Disconnect the negative battery terminal.
(2) Disconnect the passenger’s (front) air bag module 

connector C-14.

(3) Disconnect the connector while sliding the C-14 wiring 

harness side connector to the direction of the arrow.

(4) Connect special tool MB991865 to special tool MB991866.

CAUTION

Do not insert a probe into the terminal from its front side 
directly, as the connector contact pressure may be weak-
ened.
(5) Insert special tool MB991866 into the harness side 

connector C-14 (terminal No.1 and 2 <1st squib> or 
terminal No.3 and 4 <2nd squib>) by backprobing.

(6) Connect the negative battery terminal.

CAUTION

Always DTC B1B0E is set when checking DTC B1B0A. This 
is because the second side terminal is isolated when 
checking it. DTC B1B0E is set but this is not a fault. In 
addition, always DTC B1B0A is set when checking DTC 
B1B0E because the first side terminal is isolated. 
(7) Erase the diagnostic trouble code memory, and check the 

diagnostic trouble code.

Q: Is the checked DTC set?

YES : Go to Step 4.
NO :  Replace the passenger's air bag module (Refer to 

P.52B-393

). Then go to Step 5.

AC306561

Passenger's (front) air bag 
module connector C-14

BI

AC306760AU

MB991865
(Dummy resistor: 3    )

MB991866 
(Resistor harness)

C-14 Harness 

side connector

C-14 Passenger's (front) 

air bag module connector

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-86

STEP 4. Check the harness for open circuit between 
SRS-ECU connector C-37 (terminal No.7 and 8 <1st squib> 
or terminal No.11 and 12 <2nd squib>) and the passenger's 
air bag module connector C-14 (terminal No.2 and 1 <1st 
squib> or terminal No.4 and 3 <2nd squib>).
(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-37 SRS-ECU connector.

DANGER

To prevent the air bag from deploying unintentionally, 
disconnect the passenger’s (front) air bag module 
connector C-14 to short the squib circuit.

(3) Disconnect the passenger’s (front) air bag module 

connector C-14.

(4) Disconnect the connector while sliding the C-14 wiring 

harness side connector to the direction of the arrow.

AC506734

A

AD

Lock lever

AC306561

Passenger's (front) air bag 
module connector C-14

BI