Code No.B1412: Passenger’s (front) air bag module (squib) system (short-circuited to the earth)








OPERATION



TROUBLE JUDGEMENT



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

DIAGNOSIS PROCEDURE

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

(2)Release the claw (1) of the lock lever of B-107 passenger’s (front) air bag module connector, and lift the lock lever to the direction of the arrow (2), then remove the connector.

(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.
Insert special tool (MB991866) into the harness side connector B-107 by backprobing.
(5)Connect the negative auxiliary battery terminal.
(6)After erasing the diagnosis code memory, check the diagnosis code again.
(7)Disconnect the negative auxiliary battery terminal.

Q. Is diagnosis code B1412 set?

Go to Step 2

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

STEP 2. Resistance measurement at the B-112 SRS-ECU connector.
(1)Check that the negative auxiliary battery terminal is disconnected. If the negative auxiliary battery terminal is connected, disconnect it.
(2)Disconnect the B-112 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.
Release the claw (1) of the lock lever of B-107 passenger’s (front) air bag module connector, and lift the lock lever to the direction of the arrow (2), then remove the 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 the insulator (width: 3 mm, thickness: 0.5 mm) such as cable tie between the terminals Nos. 21 and 22, and then release the short spring.
(5)
caution Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.
Take the measurements below at the B-112 harness side connector.

  • Continuity between terminal No. 21/22 and body earth
OK: No continuity

Q. Is the check result normal?

Go to Step 3

Repair the harness wires between B-112 SRS-ECU connector (terminal No.21 and 22) and B-107 passenger’s (front) air bag module connector (terminal No.1 and 2).

STEP 3. Check whether the diagnosis code is reset.

Q. Is diagnosis code B1412 set?
Replace the SRS-ECU (Refer to ).
An intermittent malfunction is suspected (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).