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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.
- When DTC B1B08 is set in the following diagnosis, check the 1st squib circuit. When DTC
B1B0C is set, check the 2nd squib circuit.
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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
- Damaged harness wires and connectors
- Short to the ground in the passenger’s (front) air bag module (squib) harness
- Malfunction of the SRS-ECU
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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
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STEP 1. Using scan tool MB991958, diagnose the CAN bus line.
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(1)
| caution |
To prevent damage to scan tool MB991958, always turn the ignition switch
to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
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Connect scan tool MB991958. Refer to "How to connect the scan tool  ."
(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?
 Go to Step 2.
 Repair the CAN bus line (Refer to GROUP 54C, Diagnosis ).
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STEP 2. Recheck for diagnostic trouble code.
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Check again if the DTC is set.
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(2)Turn the ignition switch to the "ON" position.
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(3)Check if the DTC is set.
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(4)Turn the ignition switch to the "LOCK" (OFF) position.
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Go to Step 3.
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There is an intermittent malfunction such as poor engaged connector(s) or open
circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).
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STEP 3. Check the passenger’s (front) air bag module.
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(1)Disconnect the negative battery terminal.
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(2)Disconnect the passenger’s (front) air bag module connector C-14.
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(3)Disconnect the connector while sliding the C-14 wiring harness side connector to the direction
of the arrow.
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(4)Connect special tool MB991865 to special tool MB991866.
(5)
| caution |
Do not insert a test probe into the
terminal from its front side directly, as the connector contact pressure may be weakened.
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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.
(7)
| 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.
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Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
Q.
Is the checked DTC set?
Go to Step 4.
Replace the passenger’s (front) air bag module (Refer to ).
Then go to Step 6.
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STEP 4. Check the passenger’s (front) air bag module circuit.
Measure the resistance at the SRS-ECU connector C-37.
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(1)Disconnect the negative battery terminal.
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(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.
(3)
| 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.
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(4)Disconnect the connector while sliding the C-14 wiring harness side connector to the direction
of the arrow.
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(5)
| caution |
Insert an insulator such as a cable tie to a depth of 4 mm (0.16 inch) or more, otherwise
the short spring will not be released.
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Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between
terminals 7 and 8 <1st squib> or 11 and 12 <2nd squib>,
and the short spring to release the short spring.
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(6)Check for continuity between C-37 harness side connector terminals 7 and 8 <1st
squib> or 11 and 12 <2nd squib>, and body ground.
It should be an open circuit.
Q.
Is it open circuit?
Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
If DTC B1B08 <1st squib> B1B0C <2nd squib> sets, replace the
SRS-ECU (Refer to ). Then go to Step 6.
Go to Step 5.
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STEP 5. Check the harness wires for short circuit to ground between
the following connector.
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- SRS-ECU connector C-37 (terminal No.7 and 8) and passenger’s (front)
air bag module connector C-14 (terminal No.2 and 1) <1st squib>.
- SRS-ECU connector C-37 (terminal No.11 and 12) and passenger’s (front)
air bag module connector C-14 (terminal No.4 and 3) <2nd squib>.
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Q.
Is the check result normal?
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Go to Step 6.
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Repair the harness wires between SRS-ECU connector C-37 and passenger’s
(front) air bag module connector C-14. Then go to Step 6.
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STEP 6. Recheck for diagnostic trouble code.
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Check again if the DTC is set.
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(2)Turn the ignition switch to the "ON" position.
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(3)Check if the DTC is set.
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(4)Turn the ignition switch to the "LOCK" (OFF) position.
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Q.
Is DTC B1B08 <1st squib> B1B0C <2nd squib> set?
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Return to Step 1.
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The procedure is complete.
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