Code No.B1412: Passenger’s (front) air bag (1st squib) (earth side)
short-circuited
Code No.B1492: Passenger’s (front) air bag (2nd
squib) (earth side) short-circuited
| caution |
If diagnosis code B1412 <1st squib> or
B1492 <2nd squib> is set in the SRS-ECU, always diagnose the
CAN main bus line.
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OPERATION
- The SRS-ECU judges how severe a collision is by detecting signals from
the front impact sensors and the front air bag analogue 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.
DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set if the
passenger’s (front) air bag module (squib) wire(s) are short-circuited
to the earth.
PROBABLE CAUSES
- Damaged harness wires and connectors
- Short to the earth in the passenger’s (front) air bag module
(squib) harness
- Malfunction of the SRS-ECU
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STEP 1. M.U.T.-III CAN bus diagnostics
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Use the M.U.T.-III to diagnose the CAN bus
lines.
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Q.
Is the check result normal?
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 Go to Step 2.
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 Repair
the CAN bus line (Refer to GROUP 54D, Diagnosis  ).
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STEP 2. Check whether the diagnosis code is reset.
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Check again if the diagnosis code is
set.
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(1)Erase the diagnosis code.
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(2)Ignition: "LOCK" (OFF) position to "ON"
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(3)On completion, check that the diagnosis code is not
reset.
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Q.
Is the diagnosis code set?
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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)Slide the outer housing of the harness side
of passenger’s (front) air bag module connector D-11 in the arrow
direction shown, and disconnect the connector.
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(3)Connect special tool dummy resistor
(MB991865) to special tool resistor harness (MB991866).
(4)
| 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 D-11
(terminal No.1 and 2 <1st squib> or terminal No.3 and 4
<2nd squib>) by backprobing.
(5)Connect the negative battery
terminal.
(6)
| caution |
Always diagnosis code B1491 is set when checking
diagnosis code B1412. This is because the second side terminal is
isolated when checking it, diagnosis code B1491 is set but this is not a
fault. In addition, always diagnosis code B1411 is set when checking
diagnosis code B1492 because the first side terminal is isolated.
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Erase the diagnosis code from memory, and check the diagnosis
code.
Q.
Is the checked diagnosis code set?
Go to Step 4.
Replace the
passenger’s (front) air bag module (Refer to ). Then go to Step
5.
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STEP 4. Check the passenger’s (front) air bag module circuit.
Resistance measurement at the SRS-ECU connector D-24.
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(1)Disconnect the negative battery terminal.
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(2)Disconnect SRS-ECU connector D-24.
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(3)Slide the outer housing of the harness side
of passenger’s (front) air bag module connector D-11 in the arrow
direction shown, and disconnect the connector.
(4)
| 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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Check for continuity between D-24 harness side connector terminals
27 and 28 <1st squib> or 30 and 31 <2nd squib>, and
body earth.
OK: Open circuit
Q.
Is the check result normal?
Erase the diagnosis code from
memory, and check the diagnosis code. If diagnosis code B1412 <1st
squib> B1492 <2nd squib> sets, replace the SRS-ECU (Refer
to ). Then go to Step 5.
Replace the
harness wires between SRS-ECU connector D-24 and passenger’s (front)
air bag module connector D-11. Then go to Step 5.
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STEP 5. Check whether the diagnosis code is reset.
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Q.
Is diagnosis code B1412 <1st squib> B1492 <2nd
squib> set?
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Return to Step 1.
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The
procedure is complete.
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