DTC B1B03: Driver's Air Bag Module (1st squib) System (Short Circuit Between Squib Circuit Terminals); DTC B1B07: Driver's Air Bag Module (2nd squib) System (Short Circuit Between Squib Circuit Terminals): 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 "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 SRS-ECU connector C-37, driver's air bag module connector C-204 and clock spring connector C-208. 
   1. Disconnect the negative battery terminal.
   2. Disconnect connectors C-37, C-204 and C-208, and then reconnect them.
      • 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.
      • Slide the outer housing of the clock spring side of driver's air bag module connector C-204 in the arrow direction shown in the illustration and disconnect the connector.
   3. Connect the negative battery terminal.
   4. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
      Fig 2: Disconnecting C-37 SRS-ECU Connector

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

   Q: Is DTC B1B03 < 1st squib > or B1B07 < 2nd squib > set? 

   • YES:  Go to STEP 4 below.
   • NO:  The procedure is complete. It is assumed that DTC B1B03 < 1st squib > or B1B07 < 2nd squib > set because connector C-37, C-204 or C-208 was engaged improperly.
     Fig 3: Identifying Horn Connector, Lower Column Cover And Driver's Air Bag Module Connector

     Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
4. STEP 4. Check the driver's air bag module. 
   1. Disconnect the negative battery terminal.
   2. Slide the outer housing of the clock spring side of driver's air bag module connector C-204 in the arrow direction shown in the illustration and disconnect the connector.
      Fig 4: 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 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 No. 3 and 4 < 2nd squib >) by backprobing.
   5. Connect the negative battery terminal.
      Fig 5: Identifying Dummy Resister, Resister Harness And Air Beg Module Connector

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      CAUTION: Always DTC B1B06 is set when checking DTC B1B03. 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 B1B07 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 driver's air bag module (Refer to DRIVER'S AIR BAG MODULE AND CLOCK SPRING  ). Then go to  Step 8.
5. STEP 5. 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 C-208 harness side connector front side directly, as the connector contact pressure may be weakened.
   4. Insert special tool MB991866 into clock spring harness side connector C-208 (terminal No. 3 and 4 < 1st squib > or No. 1 and 2 < 2nd squib >) by backprobing.
   5. Connect the negative battery terminal.
      Fig 6: Checking Clock Spring

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      CAUTION: Always DTC B1B06 is set when checking DTC B1B03. 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 B1B07 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 6 below.
   • NO:  Replace the clock spring (Refer to DRIVER'S AIR BAG MODULE AND CLOCK SPRING  ). Then go to  Step 8.
6. STEP 6. Check the driver's air bag module circuit. Measure the resistance at SRS-ECU connector C-37. 
   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 7: Disconnecting C-37 SRS-ECU Connector

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      WARNING: To prevent the air bag from deploying unintentionally, disconnect clock spring connector C-208 to short the squib circuit.
   3. Disconnect 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 8: Inserting Cable Tie Between Terminals 5, 6 And Short Spring (1st Squib)

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

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
   5. Check for continuity between C-37 harness side connector terminals 5 and 6 < 1st squib > or 9 and 10 < 2nd squib >.

      It should be open circuit.

   Q: Is it open circuit? 

   • YES:  Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1B03 < 1st squib > or B1B07 < 2nd squib > set, replace the SRS-ECU (Refer to SRS CONTROL UNIT (SRS-ECU)  ). Then go to  Step 8.
   • NO:  Go to STEP 7 below.
     Fig 10: Checking Continuity Between C-37 Harness Side Connector Terminals 5 And 6 (1st Squib)

     Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
     Fig 11: Checking Continuity Between C-37 Harness Side Connector Terminals 9 And 10 (2nd Squib)

     Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
7. STEP 7. Check the harness for short circuit between the harness wire and wire. 
   • SRS-ECU connector C-37 (terminal No. 5 and 6) and clock spring connector C-208 (terminal No. 4 and 3) < 1st squib >.
   • SRS-ECU connector C-37 (terminal No. 9 and 10) and clock spring connector C-208 (terminal No. 1 and 2) < 2nd squib >.

   Q: the check result normal? 

   • YES:  Go to STEP 8 below.
   • NO:  Repair the harness wires between SRS-ECU connector C-37 and clock spring connector C-208. Then go to STEP 8 below.
8. STEP 8. 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 B1B03 < 1st squib > or B1B07 < 2nd squib > set? 

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