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




OPERATION



  • The SRS-ECU judges how severe a collision is by detecting signals from the left and right side impact sensors. If the impact is over a predetermined level, the SRS-ECU sends an ignition signal. At this time, if the side air bag safing G-sensor is on, the SRS side-airbag will inflate.
  • The ignition signal is input to the side-airbag module to inflate the side-airbag.

DIAGNOSIS CODE SET CONDITIONS



PROBABLE CAUSES
  • Open circuit in the side-airbag module (LH) (squib) circuit
  • Improper connector contact
  • Malfunction of the SRS-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check the diagnosis code by connecting a dummy resistor. (M.U.T.-III diagnosis code)
(1)Disconnect the negative battery terminal.





(2)Disconnect side-airbag module (LH) connector D-35. When disconnecting connector D-35, 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 D-35 by backprobing.
(5)Connect the negative battery terminal.
(6)Erase the diagnosis code memory, and check the diagnosis code.

Q. Is diagnosis code B1431 set?

Go to Step 2

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

STEP 2. Resistance measurement between SRS-ECU connector C-153 (terminal No.3 and 4) and the side-airbag module (LH) connector D-35 (terminal No.1 and 2).
(1)Disconnect the negative battery terminal.

(2)Disconnect SRS-ECU connector C-153.





(3)
danger To prevents the air bag from deploying unintentionally, disconnect the side-airbag module (LH) connector D-35 to short the squib circuit.
Disconnect side-airbag module (LH) connector D-35. When disconnecting connector D-35, 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 Insert an insulator such as a cable tie to a depth of 7 mm or more, otherwise the short spring will not be released.
Insert a cable tie [3 mm wide, 0.5 mm thick] between terminals 3, 4 and the short spring to 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.
Resistance measurement between the following terminals.

  • SRS-ECU connector C-153 terminal No.3 and the side-airbag module (LH) connector D-35 terminal No.1
  • SRS-ECU connector C-153 terminal No.4 and the side-airbag module (LH) connector D-35 terminal No.2
OK: Continuity (Less than 2 Ω)

Q. Are the check results normal?

Go to Step 3

Repair the harness wires between SRS-ECU connector C-153 (terminal No.3 and 4) and side-airbag module (LH) connector D-35 (terminal No.1 and2).

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 ).