DTC Troubleshooting
DTC P1078: IMT Valve Stuck in Low RPM PositionNOTE: 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. Start the engine, and let it idle.
4. Make sure the IMT VALVE CMD is CLOSED in the DATA LIST with the HDS.
Is CLOSE indicated?
YES - Go to step 5.
NO - Go to step 29.
5. Check the IMT VALVE SW in the DATA LIST with the HDS.
Is OPEN indicated?
YES - Go to step 6.
NO - Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the IMT actuator and the ECM/PCM.
6. Turn the ignition switch OFF.
7. Disconnect the IMT actuator 5P connector.
8. Turn the ignition switch ON (II).
9. Check the IMT VALVE SW in the DATA LIST with the HDS.
Is CLOSED indicated?
YES - Go to step 14.
NO - Go to step 10.
10. Turn the ignition switch OFF.
11. Jump the SCS line with the HDS.
12. Disconnect ECM/PCM connector B (24P).
13. Check for continuity between ECM/PCM connector terminal B11 and body ground.
Is there continuity?
YES - Repair short in the wire between the ECM/PCM (B11) and the IMT actuator, then go to step 25.
NO - Go to step 31.
14. Turn the ignition switch OFF.
15. Jump the SCS line with the HDS.
16. Disconnect ECM/PCM connector B (24P).
17. Check for continuity between ECM/PCM connector terminal B4 and body ground.
Is there continuity?
YES - Repair short in the wire between the ECM/PCM (B4) and the IMT actuator, then go to step 25.
NO - Go to step 18.
18. Connect IMT actuator 5P connector terminal No. 5 to body ground with a jumper wire.
19. Check for continuity between ECM/PCM connector terminal B4 and body ground.
Is there continuity?
YES - Go to step 20.
NO - Repair open in the wire between the ECM/PCM (B4) and the IMT actuator, then go to step 25.
20. Check for continuity between ECM/PCM connector terminal B3 and body ground.
Is there continuity?
YES - Repair short in the wire between the ECM/PCM (B3) and the IMT actuator, then go to step 25.
NO - Go to step 21.
21. Connect IMT actuator 5P connector terminal No. 4 to body ground with a jumper wire.
22. Check for continuity between ECM/PCM connector terminal B3 and body ground.
Is there continuity?
YES - Go to step 23.
NO - Repair open in the wire between the ECM/PCM (B3) and the IMT actuator, then go to step 25.
23. Remove the IMT actuator.
24. Move the IMT valve by hand.
Does it move smoothly?
YES - Substitute a known-good IMT actuator, then go to step 25 and recheck. If DTC P1077 is not indicated, replace the IMT actuator, then go to step 25. If DTC P1077 is indicated, go to step 31.
NO - Remove the engine cover, and repair the stuck valve. If necessary, replace the intake manifold, then go to step 25.
25. Reconnect all connectors.
26. Turn the ignition switch ON (II).
27. Reset the ECM/PCM with the HDS.
28. Do the ECM/PCM idle learn procedure.
29. Check for Temporary DTCs or DTCs with the HDS.
Is DTC P1077 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 30.
30. Monitor the OBD STATUS for DTC P1077 in the DTCs MENU with the HDS.
Does the screen indicate PASSED?
YES - Troubleshooting is complete. If any other Temporary DTCs or DTCs were indicated in step 29, go to the indicated DTCs 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, keep idling until a result comes on.
31. Reconnect all connectors.
32. Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM.
33. Check for Temporary DTCs or DTCs with the HDS.
Is DTC P1077 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, then recheck. If the ECM/PCM was substituted, go to step 1.
NO - Go to step 34.
34. Monitor the OBD STATUS for DTC P1077 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. If any other Temporary DTCs or DTCs were indicated in step 33, go to the indicated DTCs 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, then recheck. If the ECM/PCM was substituted, go to step 1. If the screen indicates NOT COMPLETED, keep idling until a result comes on.