Mitsubishi Evolution X. Manual — part 694
SRS AIR BAG DIAGNOSIS
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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-223
CAUTION
If DTC B1C3A 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
• Improper connector contact
• Open circuit in the driver's seat belt pre-tensioner
(squib) circuit
• 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
• MB991884: Resister harness
AC708951AD
Connector: C-36
C-36 (Y)
AC708955AF
Connector: D-25
D-25 (B)
SRS AIR BAG DIAGNOSIS
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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-224
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
."
(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,
).
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
).
AC608435
Data link connector
MB991827
MB991824
MB991910
AB
SRS AIR BAG DIAGNOSIS
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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-225
STEP 3. Check the driver's seat belt pre-tensioner.
(1) Disconnect the negative battery terminal.
(2) Disconnect driver's seat belt pre-tensioner connector D-25.
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-25 harness side
connector.
(5) Connect the negative battery terminal.
(6) Erase diagnostic trouble code memory, and then check the
diagnostic trouble code.
Q: Is DTC B1C3A set?
YES : Go to Step 4.
NO : Replace the driver's seat belt with pre-tensioner
(Refer to
). Then go to Step 5.
AC608959
AC
Pre-tensioner
Harness side
connector
Locking
button
Flat-tipped
screwdriver
AC301553CB
D-25 Harness side
connector
MB991884
(Resistor harness)
MB991865
(Dummy resistor: 3 )
SRS AIR BAG DIAGNOSIS
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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-226
STEP 4. Check the harness for open circuit between
SRS-ECU connector C-36 (terminal No.45 and 46) and the
driver's seat belt pre-tensioner D-25 (terminal No.1 and 2).
(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 seat belt pre-tensioner from deploying
unintentionally, disconnect the driver’s seat belt
pre-tensioner connector D-25 to short the squib cir-
cuit.
(3) Disconnect SRS-ECU connector C-36 and driver's seat belt
pre-tensioner connector D-25, and measure at the wiring
harness side. For connector D-25, 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.
AC507645
A
AC
Lock lever
AC608959
AC
Pre-tensioner
Harness side
connector
Locking
button
Flat-tipped
screwdriver
AC507303 CC
A
A
C-36 Harness side
connector (front view)
Section
A - A
Cable tie
Short spring
4 mm (0.16 inch) or more
Terminal
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