DTC P1787 (P0742): Torque Converter Clutch System (Stuck On): Diagnosis

Required Special Tools: 

• MB991958: Scan Tool (M.U.T.-III Sub Assembly)
  • MB991824: 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, read the A/T diagnostic trouble code. 
   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 to the data link connector.
   2. Turn the ignition switch to the "ON" position.
   3. Check for A/T diagnostic trouble code.
   4. Turn the ignition switch to the "LOCK" (OFF) position.

      Q: Is DTC P1778 (P0743) set? 

      1. YES:  Refer to , DTC P1778 (P0743): TORQUE CONVERTER CLUTCH SOLENOID VALVE SYSTEM .
      2. NO:  Go to Step 2.
         Fig 1: Connecting Special Tool MB991910 To Data Link Connector

         Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
2. STEP 2. Using scan tool MB991958, check data list item 10: Amount of Torque Converter Clutch Slippage. 
   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 to the data link connector.
   2. Start the engine. (Warming up engine)
   3. Set scan tool MB991958 to the data reading mode.
      • Item 10: Torque Converter Clutch Amount of Slippage.
        • Driving at a constant speed of 60 km/h (37 mph), the display should be "-10 to 10 r/min."
        • If the accelerator pedal is released, the display on the scan tool changes (50 km/h (31 mph) and less).
   4. Turn the ignition switch to the "LOCK" (OFF) position.

      Q: Is the torque converter clutch slippage within the specified range? 

      1. YES:  It can be assumed that this malfunction is intermittent. Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION .
      2. NO:  Go to Step 3.
         Fig 2: Connecting Special Tool MB991910 To Data Link Connector

         Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
3. STEP 3. Replace the PCM. 
   1. Replace the PCM. When the PCM is replaced, register the encrypted code. Refer to ENCRYPTED CODE REGISTRATION CRITERIA TABLE .
   2. Test drive the vehicle.
   3. Check for A/T diagnostic trouble code.

      Q: Is DTC P1787 (P0742) set? 

      1. YES:  Go to Step 4.
      2. NO:  The procedure is complete.
4. STEP 4. Replace the valve body. 
   1. Replace the valve body. Refer to TRANSAXLE <4A/T> or Refer to TRANSAXLE <5A/T>.
   2. Test drive the vehicle.
   3. Check for A/T diagnostic trouble code.

      Q: Is DTC 53 set? 

      1. YES:  Replace the Torque Converter. Refer to TRANSAXLE <4A/T> or Refer to TRANSAXLE <5A/T>.
      2. NO:  The procedure is complete.
         Fig 3: Identifying Valve Body Assembly

         Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.