DTC P1786 (P0741): Torque Converter Clutch System (Stuck Off): Diagnosis

WARNING: This page is about a different variant/trim than selected.

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

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 P1766 (P0715) or P1778 (P0743) set?
  1. YES <DTC P1766 (P0715) set>: Refer to , DTC P1766 (P0715): INPUT SHAFT SPEED SENSOR SYSTEM .
  2. YES <DTC P1778 (P0743) set>: Refer to , DTC P1778 (P0743): TORQUE CONVERTER CLUTCH SOLENOID VALVE SYSTEM .
  3. NO: Go to Step 2.
    
    Fig 1: Connecting Special Tool MB991910 To Data Link Connector
    Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
STEP 2. Using scan tool MB991958, check data list item 7: Torque Converter Clutch Solenoid Valve Duty%.
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 7: Torque Converter Clutch Solenoid Valve Duty%.
    - When driving at constant speed of 60 km/h (37 mph), the display should be "70 - 99.6%" (Gear range: 3rd gear <4A/T>, 4th gear <5A/T>).
    - When the accelerator pedal is released [at less than 50 km/h (31 mph)], the display should be "70 - 99.6% → 0%" (decreases gradually as the vehicle speed decreases) (Gear range: 3rd gear <4A/T>, 4th gear <5A/T>).
      
      Fig 2: Connecting Special Tool MB991910 To Data Link Connector
      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
4. Turn the ignition switch to the "LOCK" (OFF) position.
  Q: Is the solenoid valve operating properly?
  1. YES: Go to Step 3.
  2. NO: Go to Step 5.
STEP 3. Using scan tool MB991958, check data list item 10: Torque Converter Clutch Amount of 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 clutch operating properly?
  1. YES: Go to Step 4.
  2. NO: Go to Step 5.
    
    Fig 3: Connecting Special Tool MB991910 To Data Link Connector
    Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
STEP 4. 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 P1786 (P0741) set?
  1. YES: Replace the PCM. When the PCM is replaced, register the encrypted code. Refer to ENCRYPTED CODE REGISTRATION CRITERIA TABLE .
  2. NO: The procedure is complete.
    
    Fig 4: Connecting Special Tool MB991910 To Data Link Connector
    Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
STEP 5. Check the hydraulic pressure (for torque converter).
Measure the hydraulic pressure for torque converter. Check if the hydraulic pressure is within the standard value. Refer to , HYDRAULIC PRESSURE TEST .

Q: Is the hydraulic pressure within the standard value?
1. YES: Go to Step 7.
2. NO: Go to Step 6.
STEP 6. Adjust line pressure.
Adjust line pressure. Refer to , LINE PRESSURE ADJUSTMENT . Then check the symptom.

Q: Is the symptom eliminated?
1. YES: The procedure is complete.
2. NO: Go to Step 8.
STEP 7. Replace the PCM.
When the PCM is replaced, register the encrypted code. Refer to ENCRYPTED CODE REGISTRATION CRITERIA TABLE .

Q: Is the symptom eliminated?
1. YES: The procedure is complete.
2. NO: Go to Step 8.
STEP 8. 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 52 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 5: Identifying Valve Body Assembly
    Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.