DTC B1412: Passenger's (Front) Air Bag Module (1ST Squib) System (Shorted To Squib Circuit Ground); DTC B1492: Passenger's (Front) Air Bag Module (2ND Squib) System (Shorted To Squib Circuit Ground): Diagnosis
- STEP 1. Using scan tool (M.U.T.-IIISE), diagnose the CAN bus line. CAUTION: To 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 ."
- Turn the ignition switch to the "ON" position.
- Diagnose the CAN bus line.
- Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the CAN bus line found to be normal?
YES : Go to Step 2.
NO : Repair the CAN bus line (Refer to DIAGNOSIS ).
- STEP 2. Recheck for diagnostic trouble code.
Check again if the DTC is set.
- Erase the DTC.
- Turn the ignition switch to the "ON" position.
- Check if the DTC is set.
- 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 (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
- STEP 3. Diagnosis check by dummy resistor connection.
- Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
- Use the flat-tipped screwdriver to pull out the locking button of wiring harness side connector, and release the lock.
- Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991884).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 harness side connector ASQ+, ASQ- line <B1412>.
Insert the resistor harness probe from the back of harness side connector AQ2+, AQ2- line <B1492>.
- Connect the negative battery terminal.CAUTION: Always DTC B1492 is set when checking DTC B1412. This is because the second side terminal is isolated when checking it. DTC B1492 is set but this is not a fault. In addition, always DTC B1412 is set when checking DTC B1492 because the first side terminal is isolated.
- Erase the DTC memory, and check the diagnostic trouble code.
- Disconnect the negative battery terminal.
Q: Is the DTC set?
YES : Go to Step 4.
NO : Replace the passenger's (front) air bag module (Refer to PASSENGER'S (FRONT) AIR BAG MODULE ).
- STEP 4. Resistance measurement at the SRS-ECU connector.
- Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
- Disconnect the SRS-ECU connector.
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.CAUTION: The 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 (3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick) such as cable tie between the ASQ+, ASQ- line, and then release the short spring <B1412>.
Insert an insulator (3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick) such as cable tie between the AQ2+, AQ2- line, and then release the short spring <B1492>.
- Take the measurements below at the harness side connector.
- Continuity between ASQ+, ASQ- line and body ground <B1412>
OK: No continuity
- Continuity between AQ2+, AQ2- line and body ground <B1492>
OK: No continuity
- Continuity between ASQ+, ASQ- line and body ground <B1412>
Q: Is the check result normal?
YES : Go to Step 5.
NO : Repair ASQ+, ASQ- line <B1412> or AQ2+, AQ2- line <B1492> between the SRS-ECU connector and the passenger's (front) air bag module connector.
- STEP 5. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
Check again if the DTC is set.
- Erase the DTC.
- Turn the ignition switch to the "ON" position.
- Check if the DTC is set.
- Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC B1412 (1st squib) or B1492 (2nd squib) set?
YES : Replace SRS-ECU (Refer to SRS CONTROL UNIT (SRS-ECU) ).
NO : Intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).