Mitsubishi Outlander GS45X. Manual - part 1438

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-247

DTC B1C39: Driver's Seat Belt Pre-tensioner (Squib) System (Shorted to Squib Circuit Power Supply)

CAUTION

If DTC B1C39 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 seat belt 
pre-tensioner (squib).

.

TROUBLESHOOTING HITS

• Damaged wiring harnesses or connectors

• Short to the power supply in the driver's seat belt 

pre-tensioner (squib) harness

• Malfunction of the SRS-ECU

: CONNECTOR COUPLED: ON
  CONNECTOR UNCOUPLED: OFF

NOTE

Seat Belt Pre-Tensioner (Driver's side) (Squib) Circuit

SRS-ECU

SEAT BELT 
PRE-TENSIONER 
(LH)

CONNECTOR 
LOCK SWITCH

CONNECTOR 
LOCK 
SWITCH

AC901076

C-27 (Y)

AC

Connector: C-27

AC901080AD

Connector: D-121

D-121 (B)

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

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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-17

).

ZC501967

AC404789

AC701411AB

MB991824

MB991827

MB991910

Data link 
connector

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

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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 :  Go to Step 6.

STEP 3. Check the driver's seat belt pre-tensioner. (Using 
scan tool MB991958, read the diagnostic trouble code.)
(1) Disconnect the negative battery terminal.
(2) Disconnect driver's seat belt pre-tensioner connector 

D-121. 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.

(3) Connect special tool MB991865 to special tool MB991884.
(4) Connect special tool MB991884 to the D-121 harness side 

connector.

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

diagnostic trouble code.

Q: Is DTC B1C39 set?

YES : Go to Step 4.
NO :  Replace the driver's seat belt with pre-tensioner. 

(Refer to 

P.52B-457

). Then go to Step 6.

ZC501967

AC404789

AC701411AB

MB991824

MB991827

MB991910

Data link 
connector

AC507550AE

Seat belt 
pre-tensioner

Harness side
connector

Locking 
button

Flat-tipped
screwdriver

AC301553 BE

Harness side 
connector

MB991865

(Dummy resistor: 3    )

MB991884 

(Resistor harness)

SRS AIR BAG DIAGNOSIS

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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

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STEP 4. Check the driver's seat belt pre-tensioner circuit. 
Measure the voltage at the SRS-ECU connector C-27.
(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-27 SRS-ECU connector.

DANGER

To prevent the seat belt pre-tensioner from deploying 
unintentionally, disconnect the driver’s seat belt 
pre-tensioner connector D-121 to short the squib cir-
cuit.

(3) Disconnect driver's seat belt pre-tensioner connector 

D-121. 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.

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 45, 46 and the short spring to 
release the short spring.

(5) Connect the negative battery terminal.
(6) Ignition switch: "ON".

AC507645

A

AC

Lock lever

AC507550AE

Seat belt 
pre-tensioner

Harness side
connector

Locking 
button

Flat-tipped
screwdriver

AC507303AN

A

A

C-27 Harness side
connector (front view)

Section
A - A

Cable tie

Short spring

4 mm or more

Terminal