Code No.B1431 Left side-airbag module (squib) system (open circuit of squib circuit)


caution If the diagnosis code B1431 is set to SRS-ECU, be sure to diagnose the CAN bus line.

OPERATION


In case of side collision, when the impact exceeding the threshold is applied to the vehicle, and when the impact is simultaneously detected (turned ON) by the side impact sensor as well as by the analogue G-sensor in SRS-ECU, the electric current is supplied from SRS-ECU to the side-airbag module (squib) of impacted side.

TROUBLE JUDGEMENT


The code is set when the open circuit occurs to the SRS-ECU side-airbag module (squib) circuit.

PROBABLE CAUSES



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. Is the diagnosis code No. B1431 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)Disconnect the left side-airbag module 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 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 left side-airbag module harness side connector.
(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 the diagnosis code No. B1431 set?

Go to Step 4.

Replace the front seatback pad and frame assembly (Refer to ).

STEP 4. Resistance measurement at the SRS-ECU connector and the left side-airbag module 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 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 left side-airbag module 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 SLS-, SLS+ line and the short spring, and then release the short spring.
(5)
caution Do not insert a test probe directly into the terminal of left side-airbag module harness side connector from the connector front side as the connector contact pressure may be weakened.
Take the measurements below at the SRS-ECU and left impact sensor harness side connectors.

  • Continuity SLS- line between SRS-ECU connector and left side-airbag module connector
  • Continuity SLS+ line between SRS-ECU connector and left side-airbag module connector
OK: Continuity (less than 2 Ω)

Q. Is the check result normal?

Go to Step 5.

Repair the wiring harness SLS-, SLS+ line between the left side-airbag module connector and the SRS-ECU connector.

STEP 5. Check whether the diagnosis code is reset.

Q. Is the diagnosis code No. B1431 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 ).