Mitsubishi Evolution X. Manual — part 649
SRS AIR BAG DIAGNOSIS
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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-43
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 sent 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).
.
TROUBLESHOOTING HINTS
• Malfunction of the clock spring
• Damaged harness wires and connectors
• Short to the ground in the driver's 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
."
(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,
).
AC608435
Data link connector
MB991827
MB991824
MB991910
AB
SRS AIR BAG DIAGNOSIS
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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-44
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
).
SRS AIR BAG DIAGNOSIS
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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-45
STEP 3. Check the driver's air bag module.
(1) Disconnect the negative battery terminal.
(2) Slide the outer housing of the driver’ s air bag module
connector C-204 in the arrow direction shown, and
disconnect the connector.
(3) 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.
(4) Insert special tool MB991866 into clock spring side air bag
module connector C-204 (terminal No.1 and 2 <1st squib>
or terminal No.3 and 4 <2nd squib>) by backprobing.
(5) Connect the negative battery terminal.
CAUTION
Always DTC B1B06 is set when checking DTC B1B00. This
is because the second side terminal is isolated when
checking it, DTC B1B06 is set but this is not a fault. In
addition, always DTC B1B02 is set when checking DTC
B1B04 because the first side terminal is isolated.
(6) 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 driver's air bag module (Refer to
). Then go to Step 7.
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
AC306758AY
MB991865
(Dummy resistor: 3 )
MB991866
(Resistor harness)
C-204 Air bag
module connector
SRS AIR BAG DIAGNOSIS
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SUPPLEMENTAL RESTRAINT SYSTEM (SRS)
52B-46
STEP 4. Check the clock spring.
(1) Disconnect the negative battery terminal.
(2) Disconnect the clock spring connector C-208.
(3) 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.
(4) Insert special tool MB991866 into clock spring harness side
connector C-208 (terminal No. 3 and 4 <1st squib> or
terminal No. 2 and 1 <2nd squib>) by backprobing.
(5) Connect the negative battery terminal.
CAUTION
Always DTC B1B06 is set when checking DTC B1B00. This
is because the second side terminal is isolated when
checking it, DTC B1B06 is set but this is not a fault. In
addition, always DTC B1B02 is set when checking DTC
B1B04 because the first side terminal is isolated.
(6) Erase the diagnostic trouble code memory, and check the
diagnostic trouble code.
Q: Is the checked DTC set?
YES : Go to Step 5.
NO : Replace the clock spring (Refer to
). Then
go to Step 7.
AC306767
C-208 Clock spring
connector
AR
MB991865
(Dummy resistor: 3 )
MB991866
(Resistor harness)
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