LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Mitsubishi >> 2003 >> Montero XLS >> Repair and Diagnosis >> Transmission >> Automatic Trans >> Diagnostic Trouble Code Procedures >> Diagnostic Trouble Code Procedures <Automatic Transmission> >> DTC 54: A/T Control Relay System >> Diagnosis
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC 54: A/T Control Relay System: Diagnosis

Required Special Tool: 

  1. STEP 1. Using scan tool MB991502, check data list item 54: A/T Control Relay Output Voltage. 
    CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
    1. Connect scan tool MB991502 to the data link connector.
      Fig 1: Connecting Scan Tool MB991502 To Data Link Connector
      G01850844Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    2. Turn the ignition switch to the "ON" position.
    3. Set scan tool MB991502 to data reading mode for item 54, A/T Control Relay Output Voltage.
      • The voltage should equal battery positive voltage.
    4. Turn the ignition switch to the "LOCK" (OFF) position.

    Q: Is the measured voltage equal battery positive voltage? 

    1. YES :  It can be assumed that this malfunction is intermittent. Refer to HOW TO USE TROUBLESHOOTING/INSPECTION SERVICE POINTS - How to Cope with Intermittent Malfunction.
    2. NO :  Go to Step 2.
  2. STEP 2. Check the A/T control relay. 
    1. Remove the A/T control relay (A/T control relay connector D-13).
      Fig 2: Identifying A/T Control Relay Connector D-13 Location
      G01850845Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    2. Using jumper wires, connect terminal 2 to the negative battery terminal, and terminal 4 to the positive battery terminal.
    3. Measure the resistance between terminal 1 and 3 of the A/T control relay.
      • The resistance should measure less than 2 ohms.
      • Disconnect the jumper wires. The resistance between terminals 1 and 3 should measure over limits (open circuit).
      Fig 3: Checking A/T Control Relay
      G01850846Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Does the resistance measure less than 2 ohms when the relay is energized, and open circuit when the relay is de-energized? 

    1. YES :  Go to Step 3.
    2. NO :  Replace the A/T control relay.
  3. STEP 3. Check A/T control relay connector D-13 for loose, corroded or damaged terminals, or terminals pushed back in the connector. 
    Fig 4: Identifying A/T Control Relay Connector D-13 Location
    G01850847Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Are the connector and terminals in good condition? 

    1. YES :  Go to Step 4.
    2. NO :  Repair or replace the damaged components. Refer to HARNESS CONNECTOR INSPECTION .
  4. STEP 4. Measure the supply voltage at A/T control relay connector D-13. 
    1. Disconnect the A/T control relay and measure at the harness side.
      Fig 5: Identifying A/T Control Relay Connector D-13 Location
      G01850848Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    2. Measure the voltage between terminal 1 and ground.
      • The measured voltage should equal battery positive voltage.
      Fig 6: Measuring Supply Voltage At A/T Control Relay Connector
      G01850849Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Is the measured voltage equal to battery positive voltage? 

    1. YES :  Go to Step  7 .
    2. NO :  Go to Step 5.
  5. STEP 5. Check intermediate connector A-03 for loose, corroded or damaged terminals, or terminals pushed back in the connector. 
    Fig 7: Identifying Intermediate Connector A-03 Location And Terminal View
    G01850850Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Are the connector and terminals in good condition? 

    1. YES :  Go to step 6.
    2. NO :  Repair or replace the damaged components. Refer to HARNESS CONNECTOR INSPECTION .
  6. STEP 6. Check the harness for open circuit or short circuit to ground between A/T control relay connector D-13 terminal 1 and battery. 
    Fig 8: Identifying A/T Control Relay Connector D-13 Location And Terminal View
    G01850851Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Is the harness wire in good condition? 

    YES:  Go to Step  19 .

    NO :  Repair or replace the harness wire.

  7. STEP 7. Measure the resistance at A/T control relay connector D-13. 
    1. Disconnect the A/T control relay and measure at the harness side.
      Fig 9: Identifying A/T Control Relay Connector D-13 Location
      G01850852Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    2. Measure the resistance between terminal 2 and ground.
      • The resistance should measure less than 2 ohms.
      Fig 10: Measuring Resistance Between Terminal 2 And Ground
      G01850853Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Is the measured resistance less than 2 ohms? 

    1. YES :  Go to Step  10 .
    2. NO :  Go to Step 8.
  8. STEP 8. Check ground joint connector D-14 for loose, corroded or damaged terminals, or terminals pushed back in the connector. 
    Fig 11: Identifying Joint Connector D-14 Location And Terminal View
    G01850854Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Are the connector and terminals in good condition? 

    1. YES :  Go to Step 9.
    2. NO :  Repair or replace the damaged components. Refer to HARNESS CONNECTOR INSPECTION .
  9. STEP 9. Check the harness for open circuit or damage between A/T control relay connector D-13 terminal 2 and ground. 
    Fig 12: Identifying A/T Control Relay Connector D-13 Location And Terminal View
    G01850855Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Is the harness wire in good condition? 

    1. YES :  Go to Step 19.
    2. NO :  Repair or replace the harness wire.
  10. STEP 10. Measure the control voltage to A/T control relay connector D-13 by backprobing. 
    1. Remove the A/T control relay.
    2. Do not disconnect the A/T control relay and measure at the connector side.
      Fig 13: Identifying A/T Control Relay Connector D-13 Location And Terminal View - DTC 54
      G01850856Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    3. Turn the ignition switch to the "ON" position.
    4. Measure the voltage between terminal 4 and ground by backprobing.
      • The measured voltage should equal battery positive voltage.
      Fig 14: Measuring Voltage Between Terminal 4 And Ground By Backprobing
      G01850857Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    5. Turn the ignition switch to the "LOCK" (OFF) position.

    Q: Is the measured voltage equal to battery positive voltage? 

    1. YES :  Go to Step  16 .
    2. NO :  Go to Step 11.
  11. STEP 11. Measure the supply voltage at PCM connector D-136 by backprobing. 
    1. Do not disconnect connector D-136.
      Fig 15: Identifying PCM Connector D-136 Location And Terminal View
      G01850858Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    2. Turn the ignition switch to the "ON" position.
    3. Measure the voltage between terminal 127 and ground by backprobing.
      • The measured voltage should equal battery positive voltage.
      Fig 16: Measuring Voltage Between Terminal 127 And Ground By Backprobing
      G01850859Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    4. Turn the ignition switch to the "LOCK" (OFF) position.

    Q: Is the measured voltage equal to battery positive voltage? 

    1. YES :  Go to Step 12.
    2. NO :  Go to Step  14 .
  12. STEP 12. Check PCM connector D-136 for loose, corroded or damaged terminals, or terminals pushed back in the connector. 
    Fig 17: Identifying PCM Connector D-136 Location And Terminal View
    G01850860Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Are the connector and terminals in good condition? 

    1. YES :  Go to Step 13.
    2. NO :  Repair or replace the damaged components. Refer to HARNESS CONNECTOR INSPECTION .
  13. STEP 13. Check the harness for open circuit or damage between A/T control relay connector D-13 terminal 4 and PCM connector D-136 terminal 127. 
    Fig 18: Identifying A/T Control Relay Connector D-13 Location And Terminal View
    G01850861Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    Fig 19: Identifying PCM Connector D-136 Location And Terminal View
    G01850862Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Is the harness wire in good condition? 

    1. YES :  Go to Step  19 .
    2. NO :  Repair or replace the harness wire.
  14. STEP 14. Check PCM connector D-136 for loose, corroded or damaged terminals, or terminals pushed back in the connector. 
    Fig 20: Identifying PCM Connector D-136 Location And Terminal View
    G01850863Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Are the connector and terminals in good condition? 

    1. YES :  Go to Step 15.
    2. NO :  Repair or replace the damaged components. Refer to HARNESS CONNECTOR INSPECTION .
  15. STEP 15. Check for a short circuit to ground between A/T control relay connector D-13 terminal 4 and PCM connector D-136 terminal 127. 
    Fig 21: Identifying A/T Control Relay Connector D-13 Location And Terminal View
    G01850864Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    Fig 22: Identifying PCM Connector D-136 Location And Terminal View
    G01850865Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Is the harness wire in good condition? 

    1. YES :  Go to Step  19 .
    2. NO :  Repair or replace the harness wire.
  16. STEP 16. Measure the A/T control relay output voltage at PCM connector D-136 by backprobing. 
    1. Do not disconnect connector D-136.
      Fig 23: Identifying PCM Connector D-136 Location And Terminal View
      G01850866Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    2. Turn the ignition switch to the "ON" position.
    3. Measure the voltage between terminal 123 and ground by backprobing.
      • The measured voltage should equal battery positive voltage.
      Fig 24: Measuring Voltage Between Terminal 123 And Ground By Backprobing
      G01850867Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    4. Measure the voltage between terminal 124 and ground by backprobing.
      • The measured voltage should equal battery positive voltage.
      Fig 25: Measuring Voltage Between Terminal 124 And Ground By Backprobing
      G01850868Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    5. Turn the ignition switch to the "LOCK" (OFF) position.

    Q: Is the measured voltage equal to battery positive voltage between terminal 123 and ground, and between terminal 124 and ground? 

    1. YES :  Go to Step  19 .
    2. NO :  Go to Step 17.
  17. STEP 17. Check PCM connector D-136 for loose, corroded or damaged terminals, or terminals pushed back in the connector. 
    Fig 26: Identifying PCM Connector D-136 Location And Terminal View
    G01850869Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Are the connector and terminals in good condition? 

    1. YES :  Go to Step 18.
    2. NO :  Repair or replace the damaged components. Refer to HARNESS CONNECTOR INSPECTION .
  18. STEP 18. Check harness for open circuit or short circuit to ground between A/T control relay connector D-13 terminal 3 and PCM connector D-136 terminals 123, 124. 
    Fig 27: Identifying A/T Control Relay Connector D-13 Location And Terminal View
    G01850870Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    Fig 28: Identifying PCM Connector D-136 Location And Terminal View
    G01850871Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.

    Q: Is the harness wire in good condition? 

    1. YES :  Go to Step 19.
    2. NO :  Repair or replace the harness wire.
  19. STEP 19. Using scan tool MB991502, check data list item 54: A/T control relay output Voltage. 
    CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
    1. Connect scan tool MB991502 to the data link connector.
      Fig 29: Connecting Scan Tool MB991502 To Data Link Connector
      G01850872Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    2. Turn the ignition switch to the "ON" position.
    3. Set scan tool MB991502 to data reading mode for item 54, A/T Control Relay Output Voltage.
      • The voltage should equal battery positive voltage.
    4. Turn the ignition switch to the "LOCK" (OFF) position.

    Q: Is the measured voltage equal to battery positive voltage? 

    1. YES :  It can be assumed that this malfunction is intermittent. Refer to HOW TO USE TROUBLESHOOTING/INSPECTION SERVICE POINTS - How to Cope with Intermittent Malfunction.
    2. NO :  Replace the PCM.
scientia non olet · About LEMON Manuals