DTC B1402: Driver's Air Bag Module (1ST Squib) System (Shorted To Squib Circuit Ground); DTC B1482: Driver's 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 electric motor switch to the "ON" position.
- Diagnose the CAN bus line.
- Turn the electric motor 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 electric motor switch to the "ON" position.
- Check if the DTC is set.
- Turn the electric motor 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 (MB991866).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 (special tool) as shown in the illustration.
- Connect the negative battery terminal.
- After erasing the DTC memory, check the DTC again.
- Disconnect the negative battery terminal.CAUTION: Always DTC B1482 is set when checking DTC B1402. This is because the second side terminal is isolated when checking it, DTC B1482 is set but this is not a fault. In addition, always DTC B1402 is set when checking DTC B1482 because the first side terminal is isolated.
- Erase the DTC memory, and check the diagnostic trouble code.
Q: Is the checked DTC set?
YES : Go to Step 4
NO : Replace the driver's air bag module (Refer to DRIVER'S AIR BAG MODULE AND CLOCK SPRING ).
- STEP 4. Diagnosis check by dummy resistor connection.
- Check that the negative battery terminal is disconnected. If the negative battery terminal is connected, disconnect it.
- Disconnect the clock spring connector.
- Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991866).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 DQ1-, DQ1+ line <B1402>.
Insert the resistor harness probe from the back of harness side connector DQ2-, DQ2+ line <B1482>.
- Connect the negative battery terminal.
- After erasing the DTC memory, check the DTC again.
Q: Is the checked DTC set?
YES : Go to Step 5
NO : Replace the clock spring (Refer to DRIVER'S AIR BAG MODULE AND CLOCK SPRING ).
- STEP 5. 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.CAUTION: To release SRS-ECU connector short spring in the following operations, disconnect this clock spring connector, and keep the squib circuit shorted.
- Disconnect the clock spring connector.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 the insulator (width: 3 mm (0.12 inch), thickness: 0.5 mm (0.02 inch)) such as cable tie between the DQ1-, DQ1+ line, and then release the short spring <B1402>.
Insert the insulator (width: 3 mm (0.12 inch), thickness: 0.5 mm (0.02 inch)) such as cable tie between the DQ2-, DQ2+ line, and then release the short spring <B1482>.
- Take the measurements below at the SRS-ECU harness side connector.
- Continuity between DQ1-, DQ1+ line and body ground <B1402>
OK: No continuity
- Continuity between DQ2-, DQ2+ line and body ground <B1482>
OK: No continuity
- Continuity between DQ1-, DQ1+ line and body ground <B1402>
Q: Is the check result normal?
YES : Go to Step 6
NO : Repair the wiring harnesses DQ1-, DQ1+ line <B1402> or DQ2-, DQ2+ line <B1482> between the clock spring connector and the SRS-ECU connector.
- STEP 6. 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 B1402 <1st squib> or B1482 <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 ).