DTC Troubleshooting: P1078 (106)

DTC P1078:  IMT Valve Stuck in Low RPM Position

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information.

1.Turn the ignition switch ON (II).

2.Clear the DTC with the HDS.

3.Do the IMT TEST in the INSPECTION MENU with the HDS.

Is the result OK?


YES - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the IMT actuator and the ECM/PCM.n


NO - Go to 4.


4.Turn the ignition switch OFF.

5.Disconnect the IMT actuator 5P connector.

6.Turn the ignition switch ON (II).

7.Check the IMT VALVE SW in the DATA LIST with the HDS.

Is CLOSE indicated?


YES - Go to 12.


NO - Go to 8.


8.Turn the ignition switch OFF.

9.Jump the SCS line with the HDS.

10.Disconnect ECM/PCM connector B (44P).

11.Check for continuity between ECM/PCM connector terminal B39 and body ground.

 

Is there continuity?


YES - Repair short in the wire between the ECM/PCM (B39) and the IMT actuator, then go to 21.


NO - Go to 28.


12.Check for continuity between ECM/PCM connector terminal B37 and body ground.

 

Is there continuity?


YES - Repair short in the wire between the ECM/PCM (B37) and the IMT actuator, then go to 21.


NO - Go to 13.

13.Check for continuity between ECM/PCM connector terminal B38 and body ground.

 

Is there continuity?


YES - Repair short in the wire between the ECM/PCM (B38) and the IMT actuator, then go to 21.


NO - Go to 14.

14.Check for continuity between IMT actuator 5P connector terminal No. 4 and ECM/PCM connector terminal B37.

 

Is there continuity?


YES - Go to 15.


NO - Repair open in the wire between the ECM/PCM (B37) and the IMT actuator, then go to 21.

15.Check for continuity between IMT actuator 5P connector terminal No. 5 and ECM/PCM connector terminal B38.

 

Is there continuity?


YES - Go to 16.


NO - Repair open in the wire between the ECM/PCM (B38) and the IMT actuator, then go to 21.

16.Remove the IMT actuator.

17.Move the IMT valve by hand.

Does it move smoothly?


YES - Go to 18.


NO - Replace the IMT valve, then go to 21.


18.Substitute a known-good IMT actuator.

19.Turn the ignition switch ON (II).

20.Do the IMT TEST in the INSPECTION MENU with the HDS.

Is the result OK?


YES - Replace the original IMT actuator, then go to 21.


NO - Go to 28.


21.Reconnect all connectors.

22.Turn the ignition switch ON (II).

23.Reset the ECM/PCM with the HDS.

24.Do the ECM/PCM idle learn procedure.

25.Do the IMT TEST in the INSPECTION MENU with the HDS.

26.Check for Temporary DTCs or DTCs with the HDS.

Are any Temporary DTCs or DTCs indicated?


YES - If DTC P1078 is indicated, check for poor connections or loose terminals at the IMT actuator and the ECM/PCM, then go to 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.


NO - Go to 27.

27.Monitor the OBD STATUS for DTC P1078 in the DTCs MENU with the HDS.

Does the screen indicate PASSED?


YES - Troubleshooting is complete.n


NO - If the screen indicates FAILED, check for poor connections or loose terminals at the IMT actuator and the ECM/PCM, then go to 1. If the screen indicates NOT COMPLETED, go to 24 and recheck.


28.Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM.

29.Do the IMT TEST in the INSPECTION MENU with the HDS.

30.Check for Temporary DTCs or DTCs with the HDS.

Are any Temporary DTCs or DTCs indicated?


YES - If DTC P1078 is indicated, check for poor connections or loose terminals at the IMT actuator and the ECM/PCM, then go to 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.


NO - If the ECM/PCM was updated, troubleshooting is complete. If the ECM/PCM was substituted, replace the original ECM/PCM.n