DTC B1031, B1032: Air Thermo Sensor System: Diagnosis

Required Special Tool: 

• 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

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 (M.U.T.-III)  ."
   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 To Data Link Connector

        Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
2. STEP 2. Recheck for diagnostic trouble code. 

   Recheck if the DTC is set.

   1. Erase the DTC.
   2. Turn the ignition switch to "ON" position.
   3. Check if the DTC is set.

      Q: Is the DTC set? 

      • YES:  Go to Step 3.
      • NO:  It can be assumed that this malfunction is intermittent. Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTIONS .
3. STEP 3. Check air thermo sensor connector C-119 and A/C-ECU connector C-19 for loose, corroded or damaged terminals, or terminals pushed back in the connector. 

   Q: Are air thermo sensor connector C-119 and A/C-ECU connector C-19 in good condition? 

   • YES:  Go to Step 4.
   • NO:  Repair or replace the connector. Refer to HARNESS CONNECTOR INSPECTION .
4. STEP 4. Check the wiring harness between A/C-ECU connector C-19 (terminal 22 and 21) and air thermo sensor connector C-119 (terminals 1 and 2). 
   • Check the sensor signal line and ground line for open and short circuit.

     Q: Is the wiring harness between A/C-ECU connector C-19 (terminal 22 and 21) and air thermo sensor connector C-119 (terminals 1 and 2) in good condition? 

     • YES:  Go to Step 5.
     • NO:  Repair the wiring harness.
5. STEP 5. Check the air thermo sensor. 

   Measure the resistance between connector terminals 1 and 2 under at least two different temperatures. The resistance values should generally match those in the graph.

   NOTE: The temperature at the check should not exceed the range in the graph.

   Q: Is the air thermo sensor in good condition? 

   • YES:  Replace the A/C-ECU. Then go to Step 6.
   • NO:  Replace the air thermo sensor. Then go to Step 6.
     Fig 2: Air Thermo Sensor Temperature Graph

     Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
6. STEP 6. Recheck for diagnostic trouble code. 

   Check again if the DTC is set.

   1. Connect scan tool MB991958 to the data link connector
   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:  Return to Step  1.
      • NO:  The procedure is complete.