Code No. B1451: Left curtain air bag module (squib) system (open circuit of squib circuit)


caution If diagnosis code No. B1451 is set in the 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 curtain air bag module (squib) of impacted side.

TROUBLE JUDGEMENT


The code is set when the open circuit occurs to the SRS-ECU curtain 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. Check whether the diagnosis code is set again.
(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 diagnosis code No. B1451 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 D-17 curtain air bag module connector to the direction of the arrow. After releasing the lock, disconnect the connector.

(3)Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991884).
(4)Connect special tool resistor harness (MB991884) to left curtain air bag module 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 diagnosis code No. B1451 set?

Go to Step 4.

Replace the left curtain air bag module.

STEP 4. Resistance measurement at the SRS-ECU connector and the left curtain air bag module connector
(1)Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
(2)Disconnect the SRS-ECU connector.

(3)
danger To release SRS-ECU wiring harness side connector short spring in the following operations, disconnect curtain air bag module connector in advance, and keep the squib circuit shorted.
Use the flat-tipped screwdriver to pull out the locking button of left curtain air bag module connector to the direction of the arrow. After releasing the lock, 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 CLS+, CLS- line and the short spring, and release the short spring.

(5)Connect special tool resistor harness (MB991884) to the removed left curtain air bag module connector.
note When the resistor harness is connected, the terminal No. of connected side and the CLS+, CLS- line of resistor harness connector will become inverted.

(6)Take the following measurements.

  • Continuity CLS+ line between SRS-ECU wiring harness side connector and the resistor harness connector
  • Continuity CLS- line between SRS-ECU wiring harness side connector and the resistor harness connector
OK: Continuity (less than 2 Ω)

Q. Is the check result normal?

Go to Step 5.

Repair the wiring harness.

STEP 5. Check whether the diagnosis code is set again.

Q. Is diagnosis code No. B1451 set?
Replace SRS-ECU.
Intermittent Malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction).