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DTC P1078: IMT Valve Stuck in Low RPM Position: (2004-2005 models)

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).
  1. Turn the ignition switch ON (II).
  2. Clear the DTC with the HDS.
  3. Start the engine and hold the engine speed above 4,000 rpm.
  4. Check the IMT VALVE CMD in the DATA LIST with the HDS.

    Is OPEN indicated? 

    1. YES  - Go to step 5.
    2. NO  - Go to step  38.
  5. Check the IMT VALVE SW in the DATA LIST with the HDS.

    Is CLOSE indicated? 

    1. YES  - Go to step 6.
    2. NO  - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the IMT actuator and the ECM/PCM.
  6. Let the engine idle, then turn the ignition switch OFF.
  7. Disconnect the IMT actuator 5P connector.
  8. Turn the ignition switch ON (II).
  9. Measure voltage between IMT actuator 5P connector terminal No. 1 and body ground.
    Fig 1: Measuring Voltage Between IMT Actuator 5P Connector Terminal 1 And Body Ground
    G03659771Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there about 5 V? 

    1. YES  - Go to step 10.
    2. NO  - Repair open in the wire between the ECM/PCM (D12) and the IMT actuator, then go to step  27.
  10. Measure voltage between IMT actuator 5P connector terminal No. 3 and body ground.
    Fig 2: Measuring Voltage Between IMT Actuator 5P Connector Terminal 3 And Body Ground
    G03659772Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there about 5 V? 

    1. YES  - Go to step 11.
    2. NO  - Go to step  16.
  11. Turn the ignition switch OFF.
  12. Jump the SCS line with the HDS.
  13. Disconnect ECM/PCM connector D (17P).
  14. Connect IMT actuator 5P connector terminal No. 2 to body ground with a jumper wire.
    Fig 3: Connecting IMT Actuator 5P Connector Terminal 2 To Body Ground With Jumper Wire
    G03659773Courtesy of AMERICAN HONDA MOTOR CO., INC.
  15. Check for continuity between ECM/PCM connector terminal D10 and body ground.
    Fig 4: Checking Continuity Between ECM/PCM Connector Terminal D10 And Body Ground
    G03659774Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES  - Go to step  21.
    2. NO  - Repair open in the wire between the ECM/PCM (D10) and the IMT actuator, then go to step  29.
  16. Turn the ignition switch OFF.
  17. Jump the SCS line with the HDS.
  18. Disconnect ECM/PCM connector B (24P).
  19. Connect IMT actuator 5P connector terminal No. 3 to body ground with a jumper wire.
    Fig 5: Connecting IMT Actuator 5P Connector Terminal 3 To Body Ground With Jumper Wire
    G03659775Courtesy of AMERICAN HONDA MOTOR CO., INC.
  20. Check for continuity between ECM/PCM connector terminal B11 and body ground.
    Fig 6: Checking Continuity Between ECM/PCM Connector Terminal B11 And Body Ground
    G03659776Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES  - Go to step  36.
    2. NO  - Repair open in the wire between the ECM/PCM (B11) and the IMT actuator, then go to step  29.
  21. Check for continuity between ECM/PCM connector terminal B4 and body ground.
    Fig 7: Checking Continuity Between ECM/PCM Connector Terminal B4 And Body Ground
    G03659777Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES  - Repair short in the wire between the ECM/PCM (B4) and the IMT actuator, then go to step  29.
    2. NO  - Go to step 22.
  22. Connect IMT actuator 5P connector terminal No. 5 to body ground with a jumper wire.
    Fig 8: Connecting IMT Actuator 5P Connector Terminal 5 To Body Ground With Jumper Wire
    G03659778Courtesy of AMERICAN HONDA MOTOR CO., INC.
  23. Check for continuity between ECM/PCM connector terminal B4 and body ground.
    Fig 9: Checking Continuity Between ECM/PCM Connector Terminal B4 And Body Ground
    G03659779Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES  - Go to step 24.
    2. NO  - Repair open in the wire between the ECM/PCM (B4) and the IMT actuator, then go to step  29.
  24. Check for continuity between ECM/PCM connector terminal B3 and body ground.
    Fig 10: Checking Continuity Between ECM/PCM Connector Terminal B3 And Body Ground
    G03659780Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES  - Repair short in the wire between the ECM/PCM (B3) and the IMT actuator, then go to step  29.
    2. NO  - Go to step 25.
  25. Connect IMT actuator 5P connector terminal No. 4 to body ground with a jumper wire.
    Fig 11: Connecting IMT Actuator 5P Connector Terminal 4 To Body Ground With Jumper Wire
    G03659781Courtesy of AMERICAN HONDA MOTOR CO., INC.
  26. Check for continuity between ECM/PCM connector terminal B3 and body ground.
    Fig 12: Checking Continuity Between ECM/PCM Connector Terminal B3 And Body Ground
    G03659782Courtesy of AMERICAN HONDA MOTOR CO., INC.

    Is there continuity? 

    1. YES  - Go to step 27.
    2. NO  - Repair open in the wire between the ECM/PCM (B3) and the IMT actuator, go to step  29.
  27. Remove the IMT actuator (see IMT ACTUATOR REPLACEMENT  ).
  28. Move the IMT valve by hand.

    Does it move smoothly? 

    1. YES  - Substitute a known-good IMT actuator (see IMT ACTUATOR REPLACEMENT  ), then go to step 29 and recheck. If DTC P1078 is not indicated, replace the IMT actuator (see IMT ACTUATOR REPLACEMENT  ), then go to step 29. If DTC P1078 is indicated, go to step  36.
    2. NO  - Remove the intake manifold cover (see step 1 in REMOVAL ), and repair the stuck valve. If necessary, replace the intake manifold (see INTAKE MANIFOLD REMOVAL AND INSTALLATION ), then go to step 29.
  29. Reconnect all connectors.
  30. Turn the ignition switch ON (II).
  31. Reset the ECM/PCM with the HDS.
  32. Do the ECM/PCM idle learn procedure (see ECM/PCM IDLE LEARN PROCEDURE ).
  33. Start the engine. Hold the engine speed at 4,000 rpm for 10 seconds, then let it idle.
  34. Check for Temporary DTCs or DTCs with the HDS.

    Are any Temporary DTCs or DTCs indicated? 

    1. YES  - If DTC P1078 is indicated, check for poor connections or loose terminals at the IMT actuator and the ECM/PCM, then go to step  1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.
    2. NO  - Go to step 35.
  35. Monitor the OBD STATUS for DTC P1078 in the DTCs MENU with the HDS.

    Does the screen indicate PASSED? 

    1. YES  - Troubleshooting is complete.
    2. NO  - If the screen indicates FAILED, check for poor connections or loose terminals at the IMT actuator and the ECM/PCM, then go to step  1. If the screen indicates NOT COMPLETED, go to step  32 and recheck.
  36. Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM (see HOW TO TROUBLESHOOT CIRCUITS AT THE ECM/PCM ).
  37. Start the engine. Hold the engine speed at 4,000 rpm for 10 seconds, then let it idle.
  38. Check for Temporary DTCs or DTCs with the HDS.

    Are any Temporary DTCs or DTCs indicated? 

    1. YES  - If DTC P1078 is indicated, check for poor connections or loose terminals at the IMT actuator and the ECM/PCM, then go to step  1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.
    2. NO  - If the ECM/PCM was updated, troubleshooting is complete. If the ECM/PCM was substituted, replace the original ECM/PCM (see ECM/PCM REPLACEMENT ).
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