DTC B1B02: Driver's Air Bag Module (1st squib) System (Squib Circuit Open); DTC B1B06: Driver's Air Bag Module (2nd squib) System (Squib Circuit Open): Diagnosis

Required Special Tools: 

• MB991958: Scan Tool (M.U.T.-III Sub Assembly)
  • MB991824: Vehicle Communication Interface (V.C.I.)
  • MB991827: M.U.T.-III USB Cable
  • MB991910: M.U.T.-III Main Harness A (Vehicles with CAN Communication System)
• MB991865: Dummy resistor
• MB991866: Resister harness

1. STEP 1. Using scan tool MB991958, diagnose the CAN bus line. 
   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. Connect scan tool MB991958. 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.

   Q: Is the CAN bus line found to be normal? 

   • YES:  Go to STEP 2 below.
   • NO:  Repair the CAN bus line (Refer to DIAGNOSIS ).
     Fig 1: Connecting Special Tool MB991910 To Data Link Connector

     Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
2. STEP 2. Recheck for 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 the DTC set? 

   • YES:  Go to STEP 3 below.
   • NO:  There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
3. STEP 3. Check the driver's air bag module. 
   1. Disconnect the negative battery terminal.
   2. Slide the outer housing of the driver' s air bag module connector C-204 in the arrow direction shown in the illustration and disconnect the connector.
      Fig 2: Sliding Outer Housing Of Driver's Air Bag Module Connector C-204

      Courtesy 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 of driver's air bag module connector C-204 (terminal No. 1 and 2 < 1st squib > or terminal No. 3 and 4 < 2nd squib >) by backprobing.
   5. Connect the negative battery terminal.
      Fig 3: Inserting Special Tool Mb991866 Into Clock Spring Side Of Driver's Air Bag Module Connector C-204

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      CAUTION: Always DTC B1B06 is set when checking DTC B1B02. This is because the second side terminal is isolated when checking it. DTC B1B06 is set but this is not a fault. In addition, always DTC B1B02 is set when checking DTC B1B06 because the first side terminal is isolated.
   6. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.

   Q: Is the checked DTC set? 

   • YES:  Go to STEP 4 below.
   • NO:  Replace the driver's air bag module (Refer to DRIVER'S AIR BAG MODULE AND CLOCK SPRING  ). Then go to  Step 6.
4. STEP 4. Check the clock spring. 
   1. Disconnect the negative battery terminal.
   2. Disconnect the clock spring connector C-208.
   3. Connect special tool MB991865 to special tool MB991866.
      CAUTION: Do not insert a probe into the terminal from its front side directly, as the connector contact pressure may be weakened.
   4. Insert special tool MB991866 into harness side of clock spring connector C-208 (terminal No. 3 and 4 < 1st squib > or terminal No. 1 and 2 < 2nd squib >) by backprobing.
   5. Connect the negative battery terminal.
      Fig 4: Checking Clock Spring

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      CAUTION: Always DTC B1B06 is set when checking DTC B1B02. This is because the second side terminal is isolated when checking it. DTC B1B06 is set but this is not a fault. In addition, always DTC B1B02 is set when checking DTC B1B06 because the first side terminal is isolated.
   6. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.

   Q: Is the checked DTC set? 

   • YES:  Go to STEP 5 below.
   • NO:  Replace the clock spring (Refer to DRIVER'S AIR BAG MODULE AND CLOCK SPRING  ). Then go to  Step 6.
5. STEP 5. Check the harness for open circuit between the SRS-ECU connector C-37 and the clock spring connector C-208. 
   1. Disconnect the negative battery terminal.
   2. While pushing the part "A" indicated in the figure of the harness side connector, turn the lock lever to the direction of the arrow to release the lock lever, and disconnect the C-37 SRS-ECU connector.
      Fig 5: Disconnecting C-37 SRS-ECU Connector

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      WARNING: To prevent the air bag from deploying unintentionally, disconnect the clock spring connector C-208 to short the squib circuit.
   3. Disconnect the clock spring connector C-208.
      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.
   4. Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between terminals 5, 6 < 1st squib > or 9, 10 < 2nd squib > and the short spring to release the short spring.
      Fig 6: Inserting Cable Tie Between Terminals 5, 6 And Short Spring (1st Squib)

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      Fig 7: Inserting Cable Tie Between Terminals 9, 10 And Short Spring (2nd Squib)

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      CAUTION: Do not insert a probe into the terminal from C-208 harness side connector front side directly, as the connector contact pressure may be weakened.
   5. Check for continuity between the following terminals. It should be less than 2 ohms.
      • SRS-ECU connector C-37 (terminal No. 5) and the clock spring connector C-208 (terminal No. 4) < 1st squib >
      • SRS-ECU connector C-37 (terminal No. 6) and the clock spring connector C-208 (terminal No. 3) < 1st squib >
        Fig 8: Checking Continuity Between SRS-ECU Connector C-37 And Clock Spring Connector C-208 (1st Squib)

        Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      • SRS-ECU connector C-37 (terminal No. 9) and the clock spring connector C-208 (terminal No. 1) < 2nd squib >
      • SRS-ECU connector C-37 (terminal No. 10) and the clock spring connector C-208 (terminal No. 2) < 2nd squib >
        Fig 9: Checking Continuity Between SRS-ECU Connector C-37 And Clock Spring Connector C-208 (2nd Squib)

        Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

   Q: Does continuity exist? 

   • YES:  Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1B02 < 1st squib > or B1B06 < 2nd squib > set, replace the SRS-ECU (Refer to SRS CONTROL UNIT (SRS-ECU)  ). Then go to STEP 6 below.
   • NO:  Repair the harness wires between SRS-ECU connector C-37 and clock spring connector C-208. Then go to STEP 6 below.
6. STEP 6. Recheck for 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 B1B02 < 1st squib > or B1B06 < 2nd squib > set? 

   • YES:  Return to  Step 1.
   • NO:  The procedure is complete.