DTC Troubleshooting
DTC Troubleshooting: P1078
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. Reading and Clearing Diagnostic Trouble Codes
1. Turn the ignition switch to 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, the system is OK at this time. Check for poor connections or loose terminals at the IMT actuator and the ECM/PCM.
NO - Go to step 4.
4. Turn the ignition switch to LOCK (0).
5. Disconnect the IMT actuator 5P connector.
6. Turn the ignition switch to ON (II).
7. Check the IMT VALVE SW in the DATA LIST with the HDS.
Is CLOSE indicated?
YES - Go to step 12.
NO - Go to step 8.
8. Turn the ignition switch to LOCK (0).
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 step 21.
NO - Go to step 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 step 21.
NO - Go to step 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 step 21.
NO - Go to step 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 step 15.
NO - Repair open in the wire between the ECM/PCM (B37) and the IMT actuator, then go to step 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 step 16.
NO - Repair open in the wire between the ECM/PCM (B38) and the IMT actuator, then go to step 21.
16. Remove the IMT actuator. Service and Repair
17. Move the IMT valve by hand.
Does it move smoothly?
YES - Go to step 18.
NO - Replace the IMT valve, Service and Repair then go to step 21.
18. Substitute a known-good IMT actuator. Service and Repair
19. Turn the ignition switch to ON (II).
20. Do the IMT TEST in the INSPECTION MENU with the HDS.
Is the result OK?
YES - Replace the original IMT actuator, Service and Repair then go to step 21.
NO - Go to step 29.
21. Reconnect all connectors.
22. Turn the ignition switch to ON (II).
23. Reset the ECM/PCM with the HDS.
24. Do the ECM/PCM idle learn procedure. ECM/PCM Idle Learn Procedure
25. Do the IMT TEST in the INSPECTION MENU with the HDS.
26. Check for Pending or Confirmed DTCs with the HDS.
Is DTC P1078 indicated?
YES - Check for poor connections or loose terminals at the IMT actuator and the ECM/PCM, then go to step 1.
NO - Go to step 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. If any other Pending or Confirmed DTCs were indicated in step 26, go to the indicated DTC's troubleshooting.
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 25.
28. Reconnect all connectors.
29. Update the ECM/PCM if it does not have the latest software, ECM/PCM Update or substitute a known-good ECM/PCM. Reading and Clearing Diagnostic Trouble Codes
30. Do the IMT TEST in the INSPECTION MENU with the HDS.
31. Check for Pending or Confirmed DTCs with the HDS.
Is DTC P1078 indicated?
YES - Check for poor connections or loose terminals at the IMT actuator and the ECM/PCM. If the ECM/PCM was updated, substitute a known-good ECM/PCM, Reading and Clearing Diagnostic Trouble Codes then go to step 30. If the ECM/PCM was substituted, go to step 1.
NO - Go to step 32.
32. Monitor the OBD STATUS for DTC P0128 in the DTCs MENU with the HDS.
Does the screen indicate PASSED?
YES - If the ECM/PCM was updated, troubleshooting is complete. If the ECM/PCM was substituted, replace the original ECM/PCM. Service and Repair If any other Pending or Confirmed DTCs were indicated in step 31, go to the indicated DTC's troubleshooting.
NO - If the screen indicates FAILED, check for poor connections or loose terminals at the IMT actuator and the ECM/PCM. If the ECM/PCM was updated, substitute a known-good ECM/PCM, Reading and Clearing Diagnostic Trouble Codes then go to step 30. If the ECM/PCM was substituted, go to step 1. If the screen indicates NOT COMPLETED, go to step 30.