Code No.B1431: Side-airbag module (LH) (squib) system (open-circuited in the squib circuit)












OPERATION



TROUBLE JUDGEMENT



PROBABLE CAUSES
  • Open circuit in the side-airbag module (LH) (squib) circuit
  • Improper connector contact
  • 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 battery terminal is connected, disconnect it.

(2)Disconnect C-24 side-airbag module (LH) connector. When disconnecting C-24 connector, unlock the connector by sliding the locking button to the direction of the arrow as shown in the figure, and then disconnect 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 C-24 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 B1431 set?

Go to Step 2

Replace the front seatback assembly (LH) (Refer to ).

STEP 2. Resistance measurement between B-113 SRS-ECU connector (terminal No.3 and 4) and the C-24 side-airbag module (LH) connector (terminal No.2 and 1).
(1)Check that the negative auxiliary battery terminal is disconnected. If the negative auxiliary battery terminal is connected, disconnect it.
(2)Disconnect the B-113 SRS-ECU connector.

(3)
danger To release the connector short spring in the following operations, disconnect this side-airbag module connector, and keep the squib circuit shorted.
Disconnect the C-24 side-airbag module (LH) connector. When disconnecting the C-24 connector, unlock the connector by sliding the locking button to the direction of the arrow as shown in the figure, and then disconnect 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 an insulator (width: 3 mm, thickness: 0.5 mm) such as cable tie between the terminals Nos. 3 and 4, 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-113 and D-32 harness side connectors.

  • Continuity between B-113 SRS-ECU connector terminal No. 3 and C-24 side-airbag module connector No. 2
  • Continuity between B-113 SRS-ECU connector terminal No. 4 and C-24 side-airbag module connector No. 1
OK: Continuity (Less than 2 Ω)

Q. Is the check result normal?

Go to Step 3

Repair the harness wires between B-113 SRS-ECU connector (terminal No.3 and 4) and C-24 side-airbag module (LH) connector (terminal No.2 and 1).

STEP 3. Check whether the diagnosis code is reset.

Q. Is diagnosis code B1431 set?
Replace the SRS-ECU (Refer to ).
An intermittent malfunction is suspected (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).