DTC B1B00: Driver's Air Bag Module (1ST Squib) System (Shorted To Squib Circuit Ground); DTC B1B04: Driver's Air Bag Module (2ND Squib) System (Shorted To Squib Circuit Ground): Diagnosis

WARNING: This page is about a different car, the 2008 Mitsubishi Lancer. However, it is still accessible from the selected car via links, so may be relevant.

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 Special Tool MB991910 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 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.

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 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, and disconnect the connector.
  
  Fig 2: Identifying Driver's Air Bag Module Connector
  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.
  
  Fig 3: Connecting Special Tool MB991865 To Special Tool MB991866
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
4. Insert special tool MB991866 into clock spring side 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.
  CAUTION: Always DTC B1B06 is set when checking DTC B1B00. 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 B1B04 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.

NO : Replace the driver's air bag module (Refer to DRIVER'S AIR BAG MODULE AND CLOCK SPRING ). Then go to Step 7.
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 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-208 (terminal No. 3 and 4 < 1st squib > or terminal No. 2 and 1 < 2nd squib >) by backprobing.
  
  Fig 4: Inserting Special Tool MB991866 Into Clock Spring 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 B1B00. 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 B1B04 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 clock spring (Refer to DRIVER'S AIR BAG MODULE AND CLOCK SPRING ). Then go to Step 7.
STEP 5. Check the driver's air bag module circuit. Measure the resistance at the 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 5: Turning Lock Lever
  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 (1st Squib)
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  
  Fig 7: Inserting Cable Tie Between Terminals (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 > and body ground.
  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 B1B00 < 1st squib > or B1B04 < 2nd squib > sets, replace the SRS-ECU (Refer to SRS CONTROL UNIT (SRS-ECU) ). Then go to Step 7.

NO : Go to Step 6.

Fig 8: Checking Continuity Between C-37 Connector Terminals 5 And 6 And Body Ground (1st Squib)
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

Fig 9: Checking Continuity Between C-37 Connector Terminals 9 And 10 And Body Ground (2nd Squib)
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
STEP 6. Check the harness for short circuit to ground between SRS-ECU connector C-37 (terminal No. 5 and 6 < 1st squib > or terminal No. 9 and 10 < 2nd squib >) and clock spring connector C-208 (terminal No. 4 and 3 < 1st squib > or terminal No. 1 and 2 < 2nd squib >).
Q: Are the harness wires between SRS-ECU connector C-37 (terminal No. 5 and 6 < 1st squib > or terminal No. 9 and 10 < 2nd squib >) and clock spring connector C-208 (terminal No. 4 and 3 < 1st squib > or terminal No. 1 and 2 < 2nd squib >) in good condition?

YES : Go to Step 7.

NO : Replace the harness wires between SRS-ECU connector C-37 and clock spring connector C-208. Then go to Step 7.
STEP 7. 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 B1B00 < 1st squib > or B1B04 < 2nd squib > set?

YES : Return to Step 1.

NO : The procedure is complete.