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DTC 21: Driver's Air Bag Module (Squib) System Fault 1 (Short Circuit between Terminals of the Squib Circuit): Diagnosis

Required Special Tools: 

  1. STEP 1. Using scan tool MB991958, read the diagnostic trouble code. 
    CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
    1. Turn the ignition switch to the "ON" position.
    2. Check if the DTC is set.
    3. Turn the ignition switch to the "LOOK" (OFF) position.

    Q: Is DTC 34 set? 

    YES:  Go to Step 2.

    NO:  Go to  Step 3.

    Fig 1: Connecting Scan Tool To Data Link Connector
    G04293884Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  2. STEP 2. Check SRS-ECU connector C-12. 

    Q: Is the connector correctly engaged? 

    YES:  Go to Step 3.

    NO:  Engage the connector correctly. Then go to  Step 8.

    Fig 2: Identifying Connector C-12 Terminals
    G04298029Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  3. STEP 3. Check SRS-ECU connector C-12, clock spring connector C-205 and driver's air bag module connector C-201 (Using scan tool MB991958, read the diagnostic trouble code). 
    1. Disconnect the negative battery terminal.
    2. Disconnect connectors C-12, C-205 and C-201, and then reconnect them.
    3. Connect the negative battery terminal.
    4. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.

    Q: Is DTC 21 set? 

    YES:  Go to Step 4.

    NO:  The procedure is complete. It is assumed that DTC 21 set as connector or C-12, C-205 or C-201 was engaged improperly.

    Fig 3: Identifying Connector C-12 Terminals
    G04298029Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    Fig 4: Disconnecting Connectors C-205 And C-201
    G04297913Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  4. STEP 4. Check the driver's air bag module (Using scan tool MB991958, read the diagnostic trouble code). 
    1. Disconnect the negative battery terminal.
    2. By sliding the A section (in the figure) of driver's air bag module connector C-201 in the arrow direction, disconnect the connector.
      Fig 5: Disconnecting Driver's Air Bag Module Connector C-201
      G04297914Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    3. Connect special tool MB991865 to special tool MB991866.
      CAUTION: Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.
    4. Insert special tool MB991866 into clock spring side air bag module connector C-201 by backprobing.
    5. Connect the negative battery terminal.
    6. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.

    Q: Is DTC 21 set? 

    YES:  Go to Step 5.

    NO:  Replace the driver's air bag module (Refer to AIR BAG MODULE(S) AND CLOCK SPRING  ). Then go to  Step 8.

    Fig 6: Inserting Special Tool Into Clock Spring Side Air Bag Module Connector C-201
    G04297915Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  5. STEP 5. Check the clock spring (Using scan tool MB991958, read the diagnostic trouble code). 
    1. Disconnect the negative battery terminal.
    2. Disconnect the clock spring connector C-205.
    3. Connect special tool MB991865 to special tool MB991866.
      CAUTION: Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.
    4. Insert special tool MB991866 into clock spring harness side connector C-205 (terminal No.3 and 4) by backprobing.
    5. Connect the negative battery terminal.
    6. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.

    Q: Is DTC 21 set? 

    YES:  Go to Step 6.

    NO:  Replace the clock spring (Refer to AIR BAG MODULE(S) AND CLOCK SPRING  ). Then go to  Step 8.

    Fig 7: Inserting Special Tool Into Clock Spring Side Air Bag Module Connector C-201
    G04297916Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  6. STEP 6. Check the driver's air bag module circuit at the SRS-ECU connector C-12. 
    1. Disconnect SRS-ECU connector C-12.
      Fig 8: Identifying Connector C-12 Terminals
      G04298029Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      WARNING: To prevent the air bag from deploying unintentionally, disconnect the clock spring connector C-205 to short the squib circuit.
    2. Disconnect the clock spring connector C-205.
      Fig 9: Disconnecting Clock Spring Connector C-205
      G04297918Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      CAUTION: Insert an insulator such as a cable tie to a depth of 4mm (0.16 inch) or more, otherwise the short spring will not be released.
    3. Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between terminals 11, 12 and the short spring to release the short spring.
      Fig 10: Identifying Cable Tie
      G04297919Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      CAUTION: Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.
    4. Check for continuity between C-12 harness connector terminals 11 and 12.

      It should be open circuit.

    Q: Does continuity exist? 

    YES:  Go to Step 7.

    NO:  Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC 21 set, replace the SRS-ECU (Refer to SRS CONTROL UNIT (SRS-ECU)  ). Then go to  Step 8.

    Fig 11: Checking Continuity Between C-12 Harness Connector Terminals 11 And 12
    G04297920Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  7. STEP 7. Check the harness for short circuit between SRS-ECU connector C-12 (terminal No.11 and 12) and clock spring connector C-205 (terminal No.3 and 4). 

    Q: Are harness wires between SRS-ECU connector C-12 (terminal No.11 and 12) and clock spring connector C-205 (terminal No.3 and 4) in good condition? 

    YES:  Go to Step 8.

    NO:  Repair the harness wires between SRS-ECU connector C-12 and clock spring connector C-205. Then go to Step 8.

    Fig 12: Identifying Connector C-12 Terminals
    G04298029Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    Fig 13: Identifying Clock Spring Connector C-205
    G04297922Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  8. STEP 8. Recheck for diagnostic trouble code (Using scan tool MB991958, read the diagnostic trouble code). 

    Check again if the DTC is set.

    1. Erase the DTC.
    2. Turn the ignition switch to the "ON" position.
    3. Check if the DTC is set.
    4. Turn the ignition switch to the "LOCK" (OFF) position.

    Q: Is DTC 21 set? 

    YES:  Return to  Step 1.

    NO:  The procedure is complete (If no malfunctions are found in all steps, an intermittent malfunction is suspected. Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).

    Fig 14: Connecting Scan Tool To Data Link Connector
    G04293884Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
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