DTC B1B1B: Curtain Air Bag Module (LH) (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 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 "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 MALFUNCTIONS ).
STEP 3. Check SRS-ECU connector C-30, curtain air bag module (LH) connector F-24 and intermediate connector D-12.
1. Disconnect the negative battery terminal.
2. While pressing the part A in the illustration of the C-30 SRS-ECU harness side connector, turn the lock lever toward the arrow direction to release the lock lever. Then, disconnect the connector and reconnect it.
  
  Fig 2: Turning Lock Lever
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
3. Disconnect the F-24 connectors, and then reconnect it. Use a flat-tipped (-) screwdriver to pull out the F-24 curtain air bag module harness side connector locking button toward the arrow direction, release the lock, and then disconnect the connector.
  
  Fig 3: Disconnecting Curtain Air Bag Wiring Harness Connector
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
4. Disconnect the D-12 connector's, and then reconnect them. Unlock the connector by sliding the locking button to the direction of the arrow as shown in the illustration , and then disconnect the connector.
5. Connect the negative battery terminal.
6. After erasing the diagnostic trouble code memory, check the diagnostic trouble code again.
7. Disconnect the negative battery terminal.
Q: Is DTC B1B1B set?
- YES: Go to Step 4.
- NO: Intermittent Malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
  
  Fig 4: Disconnecting D-12 Intermediate Connector Unlock Connector
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
STEP 4. Check by dummy resistor connection.
1. Disconnect the negative battery terminal.
2. Disconnect the D-12 intermediate connector unlock the connector by sliding the locking button to the direction of the arrow as shown in the illustration , and then disconnect the connector.
  
  Fig 5: Disconnecting D-12 Intermediate Connector Unlock 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.
4. Insert the probe of resistor harness, to which the dummy resistor is installed, from the back of D-12 intermediate connector (floor harness side).
5. Connect the negative battery terminal.
6. After erasing the diagnostic trouble code memory, check the diagnostic trouble code again.
Q: Is DTC B1B1B set?
- YES: Go to Step 5.
- NO: Go to Step 6.
  
  Fig 6: Connecting Special Tool MB991865 To Special Tool MB991866
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
STEP 5. Resistance measurement at the C-30 SRS-ECU connector.
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-30 SRS-ECU connector.
  WARNING: To prevent the air bag from deploying unintentionally, disconnect the intermediate connector D-12 to short the squib circuit.
  
  Fig 7: Turning Lock Lever
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
3. Disconnect the D-12 intermediate connector unlock the connector by sliding the locking button to the direction of the arrow as shown in the illustration , and then disconnect the connector.
  CAUTION: The short spring may not be released due to the insufficient insertion. Therefore, insert the insulator for 4 mm (0.6 inch) or more.
  
  Fig 8: Disconnecting D-12 Intermediate Connector Unlock Connector
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
4. Insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between terminal 41, 42 and the short spring to release the short spring.
  
  Fig 9: Inserting Cable Tie Wide Thick Between Terminal 41, 42 And Short Spring
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
5. Check for continuity between the C-30 wiring harness side connector terminal No. 41 and No. 42. It should be open circuit.
Q: Is it open circuit?
- YES: Go to Step 7.
- NO: Repair the wiring harness.
  
  Fig 10: Checking Continuity Between C-30 Wiring Harness Side Connector Terminal 41 And 42
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
STEP 6. Short circuit check between the F-24 curtain air bag module harness side connector and the D-12 intermediate harness.
1. Disconnect the negative battery terminal.
  WARNING: To prevent the air bag from deploying unintentionally, disconnect the curtain air bag module connector F-24 to short the squib circuit.
2. Disconnect curtain air bag module (LH) F-24. Use a flat-tipped screwdriver to unlock the locking button at the harness side connector by withdrawing it toward you in two stages, and then disconnect the connector.
  
  Fig 11: Disconnecting Curtain Air Bag Wiring Harness Connector
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
3. Disconnect the D-12 intermediate connector unlock the connector by sliding the locking button to the direction of the arrow as shown in the illustration , and then disconnect the connector.
  
  Fig 12: Disconnecting D-12 Intermediate Connector Unlock Connector
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
4. Because the short spring is installed to the D-12 intermediate connector (curtain air bag harness side), insert a cable tie [3 mm (0.12 inch) wide, 0.5 mm (0.02 inch) thick] between terminals 1, 2 and the short spring to release the short spring.
  
  Fig 13: Inserting Cable Tie Wide Thick Between Terminals 1, 2 And Short Spring
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
  
  CAUTION: Do not insert a probe into the terminal from its front side directly, as the connector contact pressure may be weakened.
5. Check for continuity between the D-12 intermediate connector (curtain air bag harness side) terminal No. 1 and 2.
  It should be open circuit.
Q: Is it open circuit?
- YES: Replace the curtain air bag module (LH) (Refer to CURTAIN AIR BAG MODULE(S) ). Then go to Step 7.
- NO: Repair the wiring harness.
  
  Fig 14: Checking Continuity Between D-12 Intermediate Connector (Curtain Air Bag Harness Side) Terminal 1 And 2
  Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
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 B1B1B set?
- YES: Replace SRS-ECU (Refer to SRS CONTROL UNIT (SRS-ECU) ).
- NO: Intermittent Malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).