Code No.B1411 Passenger’s (front) air bag module (squib) system (open circuit of squib circuit)


caution
  • If the diagnosis code B1411 (squib) is set to SRS-ECU, be sure to diagnose the CAN bus line.
  • Follow the diagnosis procedure below. If diagnosis code B1411 is set, check squib side circuit.

OPERATION


Only when the frontal impact exceeding the threshold is simultaneously detected (turned ON) by the front impact sensor as well as by the analogue G-sensor in SRS-ECU, the electric current is supplied from SRS-ECU to the passenger’s (front) air bag module (squib).

TROUBLE JUDGEMENT


The code is set when the open circuit occurs to the SRS-ECU passenger’s (front) air bag 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. M.U.T.-III diagnosis code.
(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. B1411 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)Use the flat-tipped screwdriver to pull out the locking button of wiring harness side connector, and release the lock, connect the connector again.

(3)Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991866).
(4)
caution Do not insert a probe directly into the passenger’s (front) air bag module terminal from the connector front side as the connector contact pressure may be weakened.
Insert the resistor harness probe from the back of passenger’s (front) air bag module harness side connector ASQ+, ASQ- line.
(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. B1411 set?

Go to Step 4.

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

STEP 4. Resistance measurement at the SRS-ECU connector and the passenger’s (front) air bag 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 harness side connector, and keep the squib circuit shorted.
Use the flat-tipped screwdriver to pull out the locking button of wiring harness side connector, and release the lock.

(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 ASQ+, ASQ- line, and then release the short spring.
(5)
caution Do not insert a probe directly into the terminal of passenger’s (front) air bag 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 connector and passenger’s (front) air bag module connector harness side connectors.

  • Continuity ASQ- line between the SRS-ECU connector and the passenger’s (front) air bag module connector.
  • Continuity ASQ+ line between the SRS-ECU connector and the passenger’s (front) air bag module connector.
OK: Continuity (less than 2 Ω)

Q. Is the check result normal?

Go to Step 5.

Repair the wiring harnesses ASQ+, ASQ- line between the passenger’s (front) air bag module connector and the SRS-ECU connector.

STEP 5. Check whether the diagnosis code is reset.

Q. Is the diagnosis code No. B1411 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 ).