DTC B1B54: Seat Belt Buckle Switch (RH) Circuit (Ground Side) Shorted; DTC B1B55: Seat Belt Buckle Switch (RH) Circuit (Power Supply Side) Shorted; DTC B1B56: Seat Belt Buckle Switch (RH) Circuit Open: Diagnosis

Required Special Tools: 

• MB991222: Probe
• 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)

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. Connect scan tool MB991958 to the data link connector.
   3. Turn the ignition switch to the "ON" position.
   4. Diagnose the CAN bus line.
   5. 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.
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.
   • 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 harness short circuit between seat belt buckle switch (passenger's side) connector D-33 and the SRS-ECU connector C-30. 
   1. Disconnect the negative battery terminal.
   2. Disconnect the seat belt buckle switch (passenger's side) connector D-33.
   3. 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.
      Fig 2: Turning Lock Lever

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
   4. Measure the resistance between terminal 55, 58 and body ground (No. B1B54 only). It should be an open circuit.
      Fig 3: Measuring Resistance Between Terminal 55, 58 And Body Ground

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
   5. Connect the negative battery terminal.
   6. Ignition switch: ON.
   7. Measure the voltage between terminal 55, 58 and body ground (No. B1B55 only).

      Voltage should measure 1 volt or less.

   Q: Is the check result normal? 

   • YES:  Go to  Step 5.
   • NO:  Go to Step 4.
     Fig 4: Measuring Voltage Between Terminal 55, 58 And Body Ground

     Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
4. STEP 4. Check the harness wires between SRS-ECU connector C-30 (terminal No. 55 and 58) and the seat belt buckle switch (passenger's side) connector D-33 (terminal No. 1 and 2) (No. B1B56 only). 

   Q: Is the check result normal? 

   • YES:  Go to  Step 6.
   • NO:  Repair the harness wires between SRS-ECU connector C-30 and the seat belt buckle switch (passenger's side) connector D-33. Then go to  Step 6.
5. STEP 5. Check the harness wires between SRS-ECU connector C-30 (terminal No. 55 and 58) and the seat belt buckle switch (passenger's side) connector D-33 (terminal No. 1 and 2). 
   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.
   3. Disconnect the seat belt buckle switch (passenger's side) connector D-33.
      CAUTION: Do not insert a probe into the terminal from D-33 harness side connector front side directly, as the connector contact pressure may be weakened.
   4. Check for continuity between the following terminals. It should be less than 2 ohms.
      • SRS-ECU connector C-30 (terminal No. 55) and the seat belt buckle switch (passenger's side) connector D-33 (terminal No. 1)
      • SRS-ECU connector C-30 (terminal No. 58) and the seat belt buckle switch (passenger's side) connector D-33 (terminal No. 2)
      Fig 5: Turning Lock Lever

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

   Q: Is the check result normal? 

   • YES:  go to Step 6.
   • NO:  Repair harness wires between SRS-ECU connector C-30 and the seat belt buckle switch (passenger's side) connector D-33.
     Fig 6: Checking Continuity Between SRS-ECU Connector C-30 (Terminal 55) And Seat Belt Buckle Switch (Passenger'S Side) Connector D-33 (Terminal 1)

     Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
6. STEP 6. Seat belt buckle switch (passenger's side) check. 

   Refer to FRONT SEAT BELT

   Q: Is the check result normal? 

   • YES:  Go to Step 7.
   • NO:  Replace the seat belt buckle switch (passenger's side) (Refer to FRONT SEAT BELT ).
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 B1B54, B1B55 or B1B56 set? 

   • YES:  Replace the SRS-ECU (Refer to SRS CONTROL UNIT (SRS-ECU)  ).
   • NO:  The procedure is complete.