Code No.B1412 Passenger’s (front) air bag module (squib) system
(shorted to squib circuit earth)
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- If the diagnosis code B1412 is set to SRS-ECU, be sure to diagnose the
CAN bus line.
- Follow the diagnosis procedure below. If diagnosis code B1412 is set,
check squib side circuit.
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Only when the frontal impact exceeding the
threshold is simultaneously detected (turned ON) by the front impact sensor
as well as by the analogue G-sensor and safing G-sensor in SRS-ECU, the
electric current is supplied from SRS-ECU to the passenger’s (front)
air bag module (squib).
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The code is set when the SRS-ECU
passenger’s (front) air bag module (squib) circuit is shorted to
earth.
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- Damaged wiring harness and connectors
- Passenger’s (front) air bag module (squib) harness shorted to
earth
- Malfunction of SRS-ECU
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STEP 1. M.U.T.-III CAN bus diagnostics.
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Use 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 54C - Troubleshooting  ).
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STEP 2. Check whether the diagnosis code is set again.
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(1)Connect the negative battery terminal.
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(2)After erasing the diagnosis code memory, check the
diagnosis code again.
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(3)Disconnect the negative battery terminal.
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Q.
Is diagnosis codes No. B1412 set?
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Go to Step 3.
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Intermittent malfunction (Refer to
GROUP 00 - How to Use Troubleshooting/Inspection Service Points
- How to Cope with Intermittent Malfunction ).
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STEP 3. Diagnosis check by dummy resistor connection.
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(1)Check that the negative battery terminal is disconnected.
If the negative battery terminal is connected, disconnect it.
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(2)Use the flat-tipped screwdriver to pull out
the locking button of wiring harness side connector, and release the
lock.
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(3)Connect special tool dummy resistor
(MB991865) to special tool resistor harness (MB991866).
(4)
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Do not insert a probe directly into the terminal
from the connector front side as the connector contact pressure may be
weakened.
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Insert the resistor harness probe from the back of harness side
connector ASQ+, ASQ- line.
(5)Connect the negative battery
terminal.
(6)After erasing the diagnosis code memory, check the
diagnosis code again.
(7)Disconnect the negative battery
terminal.
Q.
Is diagnosis code No. B1412 set?
Go to Step 4.
Replace the passenger’s (front)
air bag module (Refer to ).
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STEP 4. Resistance measurement at the SRS-ECU connector.
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(1)Check that the negative battery terminal is disconnected.
If the negative battery terminal is connected, disconnect it.
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(2)Disconnect the SRS-ECU connector.
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(3)
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To release the connector short spring in the
following operations, disconnect this harness side connector, and keep
the squib circuit shorted.
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Use the flat-tipped screwdriver to pull out the locking button of
wiring harness side connector, and release the lock.
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(4)
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The short spring may not be released due to the
insufficient insertion. Therefore, insert the insulator for 4 mm or
more.
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Insert an insulator (width: 3 mm, thickness: 0.5 mm) such as cable
tie between the ASQ+, ASQ- line, and then release the short
spring.
(5)Take the measurements below at the harness side
connector.
- Continuity between ASQ+, ASQ- line and body earth
OK: No continuity
Q.
Is the check result normal?
Go to Step 5.
Repair ASQ+, ASQ- line between
the SRS-ECU connector and the passenger’s (front) air bag module
connector.
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STEP 5. Check whether the diagnosis code is set again.
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Q.
Is diagnosis code No. B1412 set?
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Replace SRS-ECU (Refer to ).
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Intermittent malfunction (Refer to
GROUP 00 - How to Use Troubleshooting/Inspection Service Points
- How to Cope with Intermittent Malfunction ).
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