DTC B1079: Refrigerant Leaks: 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 MB991910 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 A/C pressure sensor connector A-42 and A/C controller assembly (A/C-ECU) connector C-146 for loose, corroded or damaged terminals, or terminals pushed back in the connector  .

   Q: Are A/C pressure sensor connector A-42 and A/C controller assembly (A/C-ECU) connector C-146 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 controller assembly (A/C-ECU) connector C-146 (terminals 12, 11 and 6) and A/C pressure sensor connector A-42 (terminals 3, 2 and 1)  .
   NOTE: Also check intermediate connector C-127 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-127 is damaged, repair or replace the connector as described in HARNESS CONNECTOR INSPECTION .
   • Check the sensor signal line and ground line for open or short circuit.

   Q: Is the wiring harness between A/C controller assembly (A/C-ECU) connector C-146 (terminals 12, 11 and 6) and A/C pressure sensor connector A-42 (terminals 3, 2 and 1) in good condition? 

   • YES:  Go to Step 5.
   • NO:  Repair the wiring harness.
5. STEP 5. Check the A/C pressure sensor operation  .
   1. Assemble a gauge manifold on the high pressure service valve.
   2. Disconnect the A/C pressure sensor connector and connect special tool test harness MB991658 as shown in the illustration (See Fig 3).
   3. Turn ON the engine and then turn ON the A/C switch.
      Fig 2: Identifying A/C Pressure Sensor Connector

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
      Fig 3: Checking Voltage Between A/C Pressure Sensor Terminal 2 And Ground

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
   4. At this time, check to see that the voltage of A/C pressure sensor terminal No. 2 reflects the specifications in Fig 4 .
      NOTE: The allowance shall be defined as ±5%.
      Fig 4: VS Refrigerant Pressure Out Voltage Graph

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

   Q: Is the A/C pressure sensor operating properly? 

   • YES:  Go to Step 6.
   • NO:  Replace the A/C pressure sensor. Then go to  Step 7.
6. STEP 6. Check the refrigerant level  .

   Use the refrigerant recovery station to remove all of the refrigerant, and then calculate the amount of the refrigerant and charge it.

   Q: Is the refrigerant level correct? 

   • YES:  Go to Step 7.
   • NO:  Correct the refrigerant level (Refer to ON-VEHICLE SERVICE  ). Then go to Step 7.
7. STEP 7. 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.