B1431

DTC B1431: Side-Airbag Module (LH) (Squib) System Fault 2 (Open in the Squib Circuit)













CAUTION:
If DTC B1431 is set in the combination meter, always diagnose the CAN bus lines.

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-airbag 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.

DTC SET CONDITIONS

This DTC is set if there is abnormal resistance between the input terminals of the side-airbag module (LH) (squib).

TROUBLESHOOTING HINTS

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

DIAGNOSIS

Required Special Tools:

- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A
- MB991865: Dummy resistor
- MB991866: Resister harness

STEP 1. Using scan tool MB991958, diagnose the CAN bus line.





CAUTION:
To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

(1)Connect scan tool MB991958. Refer to "How to connect the scan tool Reading and Clearing Diagnostic Trouble Codes."
(2)Turn the ignition switch to "ON" position.
(3)Diagnose the CAN bus line.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the check result satisfactory?

YES Go to Step 2

NO Repair the CAN bus lines CAN Bus Diagnostics Chart).

STEP 2. Recheck for diagnostic trouble code.





Check again if the DTC is set.
(1)Erase the DTC.
(2)Turn the ignition switch to "ON" position.
(3)Check if the DTC is set.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the DTC set?

YES Go to Step 3.

NO There is an intermittent malfunction such as poor engaged connector(s) or open circuit How to Cope With Intermittent Malfunctions).

STEP 3. Check the side-airbag module (LH). (Using scan tool MB991958, read the diagnostic trouble code.)

(1)Disconnect the negative battery terminal.





(2)Disconnect the side-airbag module (LH) connector D-23.





(3)Connect special tool MB991865 to special tool 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 D-23 harness side connector by backprobing.
(5)Connect the negative battery terminal.
(6)Erase diagnostic trouble code memory, and then check the diagnostic trouble code.

Q. Is DTC B1431 set?

YES Go to Step 4.

NO Replace the seatback frame of the front seat (LH) Front Seat Assembly Disassembly and Assembly).
Then go to Step 5.

STEP 4. Check the harness for open circuit between the SRS-ECU connector C-122 (terminal No.9 and 10) and the side-airbag module (LH) connector D-23 (terminal No.1 and 2).

(1)Disconnect the negative battery terminal.





(2)Disconnect SRS-ECU connector C-122.





(3)DANGER:
To prevent the air bag from deploying unintentionally, disconnect the side-airbag module (LH) connector D-23 to short the squib circuit.

Disconnect side-airbag module (LH) connector D-23.





(4)
CAUTION:
Insert an insulator such as a cable tie to a depth of 4mm (0.16 inch) or more, otherwise the short spring will not be released.

Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between terminals 9, 10 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.

Check for continuity between the following terminals. It should be less than 2 ohms.

- SRS-ECU connector C-122 (terminal No.9) and the side-airbag module (LH) connector D-23 (terminal No.1)
- SRS-ECU connector C-122 (terminal No.10) and the side-airbag module (LH) connector D-23 (terminal No.2)

Q. Does continuity exist?

YES Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
If DTC B1431 sets, replace the SRS-ECU (Refer to Service and Repair). Then go to Step 5.

NO Repair the harness wires between SRS-ECU connector C-122 and side-airbag module (LH) connector D-23. Then go to Step 5.

STEP 5.Recheck for diagnostic trouble code.





Check again if the DTC is set.
(1)Erase the DTC.
(2)Turn the ignition switch to the "ON" position.
(3)Check if the DTC is set.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is DTC B1431 set?

YES Return to Step 1.

NO The procedure is complete.