Code No.B1412 Passenger’s (front) air bag module (1st squib) system (shorted to squib circuit earth)
Code No.B1492 Passenger’s (front) air bag module (2nd squib) system (shorted to squib circuit earth)


caution
  • If the diagnosis code B1412 (1st squib) or B1492 (2nd squib) 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 1st squib side circuit. If diagnosis code B1492 is set, check 2nd squib side circuit.

OPERATION
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).

TROUBLE JUDGEMENT
The code is set when the SRS-ECU passenger’s (front) air bag module (squib) circuit is shorted to earth.

PROBABLE CAUSES

  • Damaged wiring harness and connectors
  • Passenger’s (front) air bag module (squib) harness shorted to earth
  • Malfunction of SRS-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics.
Use M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting ).

STEP 2. Check whether the diagnosis code is reset.
(1)Connect the negative battery terminal.
(2)After erasing the diagnosis code memory, check the diagnosis code again.
(3)Disconnect the negative battery terminal.

Q. Are diagnosis codes No. B1412 and B1492 set?
Go to Step 3.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).

STEP 3. Diagnosis check by dummy resistor connection.
(1)Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.

(2)Slide the outer housing of harness side connector in the arrow direction shown, and disconnect the C-114 harness side connector.

(3)Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991866).
(4)
caution Do not insert a probe directly into the terminal from the connector front side as the connector contact pressure may be weakened.
Insert the resistor harness probe from the back of C-114 harness side connector terminals No. 1 and 2 (1st squib) or No. 3 and 4 (2nd squib).
(5)Connect the negative battery terminal.
(6)
caution At the diagnosis code B1412 check, always the diagnosis code B1491 is set. The diagnosis code B1491 is set because the 2nd side terminal is disconnected at the time of inspection, but this does not indicate any abnormality. Also, at the time of diagnosis code B1492 check, always the diagnosis code B1411 is set because the 1st side terminals are disconnected.
After erasing the diagnosis code memory, check the diagnosis code again.
(7)Disconnect the negative battery terminal.

Q. Is the diagnosis code No. B1412 or B1492 set?

Go to Step 4.

Replace the passenger’s (front) air bag module (Refer to ).

STEP 4. Resistance measurement at the C-126 SRS-ECU connector.
(1)Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.

(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-126 SRS-ECU connector.

(3)
danger To release the connector short spring in the following operations, disconnect this harness side connector, and keep the squib circuit shorted.
Slide the outer housing of harness side connector in the arrow direction shown, and disconnect the C-114 harness side connector.


(4)
caution The short spring may not be released due to the insufficient insertion. Therefore, insert the insulator for 4 mm or more.
Insert an insulator (width: 3 mm, thickness: 0.5 mm) such as cable tie between the terminals No. 7 and 8 (1st squib) and No. 9 and 10 (2nd squib), and then release the short spring.
(5)Take the measurements below at the C-126 harness side connector.

  • Continuity between terminal No. 7/8 and body earth (1st squib)
  • Continuity between terminal No. 9/10 and body earth (2nd squib)
OK: No continuity

Q. Is the check result normal?

Go to Step 5.

Repair between the C-126 SRS-ECU connector terminal No. 7/8 and the C-114 passenger’s (front) air bag module connector terminal No. 1/2 (1st squib), and between the C-126 SRS-ECU connector terminal No. 9/10 and the C-114 passenger’s (front) air bag module connector terminal No. 4/3.

STEP 5. Check whether the diagnosis code is reset.

Q. Is the diagnosis code No. B1412 or B1492 set?
Replace SRS-ECU (Refer to ).
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).