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

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.
- NO: Repair the CAN bus line (Refer to DIAGNOSIS ).
  
  Fig 1: Connecting Scan Tool To Data Link Connector
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
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.
- 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. 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 illustration 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 below, and disconnect the connector.
3. Connect the negative battery terminal.
4. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.
Q: Is DTC B1B03 <1st squib> or B1B07 <2nd squib> set?
- YES: Go to Step 4.
- 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.
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 below, and disconnect the connector.
  
  Fig 4: 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.
  
  Fig 5: Inserting Special Tool MB991866 Into Clock Spring Side Air Bag Module Connector C-204
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
5. Connect the negative battery terminal.
  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.
- NO: Replace the driver's air bag module (Refer to DRIVER'S AIR BAG MODULE AND CLOCK SPRING ). Then go to Step 8.
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.
  
  Fig 6: Inserting Special Tool MB991866 Into Clock Spring Harness Side Connector C-208
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
5. Connect the negative battery terminal.
  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.
- NO: Replace the clock spring (Refer to DRIVER'S AIR BAG MODULE AND CLOCK SPRING ). Then go to Step 8.
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 illustration 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: Turning Lock Lever
  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 4 mm (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: Cable Tie & Short Spring (1 Of 2)
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  
  Fig 9: Cable Tie & Short Spring (2 Of 2)
  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.
  
  Fig 10: Checking Continuity Between C-37 Harness Side Connector Terminals 5 & 6
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  
  Fig 11: Checking Continuity Between C-37 Harness Side Connector Terminals 9 & 10
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
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.
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.
- NO: Repair the harness wires between SRS-ECU connector C-37 and clock spring connector C-208. Then go to Step 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.