Mitsubishi Evolution X. Manual — part 656

SRS AIR BAG DIAGNOSIS

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-71

DTC B1B08: Passenger's (Front) Air Bag Module (1st squib) System (Shorted to Squib Circuit
Ground)

DTC B1B0C: Passenger's (Front) Air Bag Module (2nd squib) System (Shorted to Squib Circuit
Ground)

CAUTION

If DTC B1B08 <1st squib> or B1B0C <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.

.

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

TSB Revision

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-72

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

• Damaged harness wires and connectors

• Short to the ground in the passenger's (front) air

bag module (squib) harness

• Malfunction of the SRS-ECU

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) 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-73

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

).

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 test probe into the terminal from its front
side directly, as the connector contact pressure may be
weakened.
(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 B1B08. 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
B1B0C 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 (front) air bag module (Refer

to

P.52B-393

). Then go to Step 6.

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-74

STEP 4. Check the passenger's (front) air bag module
circuit. Measure the resistance at the SRS-ECU connector
C-37.
(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