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DTC B1451 Curtain air bag module (LH) (squib) system (open circuit of squib circuit)
 
 
cautionIf DTC B1451 is set in 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 analog G-sensor in SRS-ECU, the electric current is supplied from SRS-ECU to the curtain air bag module (squib) of impacted side.
 
 
TROUBLE JUDGMENT
The code is set when the open circuit occurs to the SRS-ECU curtain air bag module (squib) circuit.
 
 
PROBABLE CAUSES
  • Open circuit to the curtain air bag module (squib) circuit
  • Damaged wiring harness and connector
  • Malfunction of SRS-ECU
 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-IIISE), diagnose the CAN bus line.
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-IIISE).
Connect scan tool (M.U.T.-IIISE). Refer to "How to connect the scan tool ."
(2) Turn the ignition switch to the "ON" position.
(3) Diagnose the CAN bus line.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the CAN bus line found to be normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C, Diagnosis ).
 
STEP 2. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
(1) Connect the negative battery terminal.
(2) After erasing the DTC memory, check the DTC again.
(3) Disconnect the negative battery terminal.
Is DTC 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 curtain air bag module (LH) 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 the special tool resistor harness to the curtain air bag module (LH) harness side connector.
(5) Connect the negative battery terminal.
(6) After erasing the DTC memory, check the DTC again.
(7) Disconnect the negative battery terminal.
Is DTC B1451 set?
Go to Step 4.
Replace the curtain air bag module (LH) (Refer to ).
 
STEP 4. Resistance measurement at the SRS-ECU connector and the curtain air bag module (LH) 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)
dangerTo 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 curtain air bag module (LH) connector to the direction of the arrow. After releasing the lock, disconnect the connector.
(4)
cautionThe short spring may not be released due to the insufficient insertion. Therefore, insert the insulator for 4 mm (0.16 inch) or more.
Insert an insulator [width: 3 mm (0.12 inch), thickness: 0.5 mm (0.02 inch)] 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 curtain air bag module (LH) connector.
(6) Take the measurements below at the resistor harness and SRS-ECU harness side connector.
  • Continuity CLS+ line between SRS-ECU connector and resistor harness connector
  • Continuity CLS- line between SRS-ECU connector and resistor harness connector
OK: The resistance should be 2 ohms or less
Is the check result normal?
Go to Step 5.
Repair the wiring harness CLS+, CLS- line between the SRS-ECU connector and the curtain air bag module (LH) connector.
 
STEP 5. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
Is DTC B1451 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 ).