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. Initial Inspection and Diagnostic Overview
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 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. Measure the voltage between IMT actuator 5P connector terminal No. 1 and body ground.
Is there about 5 V?
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 PCM connector C (49P).
11. Check for continuity between IMT actuator 5P connector terminal No. 1 and PCM connector terminal C11.
Is there continuity?
YES - Go to step 37.
NO - Repair open in the wire between the PCM (C11) and the IMT actuator, then go to step 30.
12. Measure the voltage between IMT actuator 5P connector terminal No. 3 and body ground.
Is there about 5 V?
YES - Go to step 17.
NO - Go to step 13.
13. Turn the ignition switch to LOCK (0).
14. Jump the SCS line with the HDS.
15. Disconnect PCM connector B (49P).
16. Check for continuity between IMT actuator 5P connector terminal No. 3 and PCM connector terminal B19.
Is there continuity?
YES - Go to step 37.
NO - Repair open in the wire between the PCM (B19) and the IMT actuator, then go to step 30.
17. Turn the ignition switch to LOCK (0).
18. Jump the SCS line with the HDS.
19. Disconnect PCM connector C (49P).
20. Check for continuity between IMT actuator 5P connector terminal No. 2 and PCM connector terminal C15.
Is there continuity?
YES - Go to step 21.
NO - Repair open in the wire between the PCM (C15) and the IMT actuator, then go to step 30.
21. Check for continuity between PCM connector terminal C48 and body ground.
Is there continuity?
YES - Repair short in the wire between the PCM (C48) and the IMT actuator, then go to step 30.
NO - Go to step 22.
22. Check for continuity between PCM connector terminal C49 and body ground.
Is there continuity?
YES - Repair short in the wire between the PCM (C49) and the IMT actuator, then go to step 30.
NO - Go to step 23.
23. Check for continuity between IMT actuator 5P connector terminal No. 5 and PCM connector terminal C48.
Is there continuity?
YES - Go to step 24.
NO - Repair open in the wire between the PCM (C48) and the IMT actuator, then go to step 30.
24. Check for continuity between IMT actuator 5P connector terminal No. 4 and PCM connector terminal C49.
Is there continuity?
YES - Go to step 25.
NO - Repair open in the wire between the PCM (C49) and the IMT actuator, then go to step 30.
25. Remove the IMT actuator. Service and Repair
26. Move the IMT valve by hand.
Does it move smoothly?
YES - Go to step 27.
NO - Remove the engine cover, Intake Manifold Removal and Installation and repair the stuck valve If needed, replace the intake manifold,. Intake Manifold Removal and Installation then go to step 30.
27. Substitute a known-good IMT actuator. Service and Repair
28. Turn the ignition switch to ON (II).
29. 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 30.
NO - Go to step 37.
30. Reconnect all connectors.
31. Turn the ignition switch to ON (II).
32. Reset the PCM with the HDS.
33. Do the PCM idle learn procedure. PCM Idle Learn Procedure
34. Start the engine. Hold the engine speed at 4,000 rpm for 10 seconds, then let it idle.
35. Check for Temporary DTCs or DTCs with the HDS.
Is DTC P1078 indicated?
YES - Check for poor connections or loose terminals at the IMT actuator and the PCM, then go to step 1.
NO - Go to step 36.
36. 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 Temporary DTCs or DTCs were indicated in step 35, 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 PCM, then go to step 1. If the screen indicates NOT COMPLETED, keep idling until a result comes on.
37. Reconnect all connectors.
38. Update the PCM if it does not have the latest software, PCM Update or substitute a known-good PCM. Initial Inspection and Diagnostic Overview
39. Start the engine. Hold the engine speed at 4,000 rpm for 10 seconds, then let it idle.
40. Check for Temporary DTCs or DTCs with the HDS.
Is DTC P1078 indicated?
YES - Check for poor connections or loose terminals at the IMT actuator and the PCM. If the PCM was updated, substitute a known-good PCM, Initial Inspection and Diagnostic Overview then go to step 39. If the PCM was substituted, go to step 1.
NO - Go to step 41.
41. Monitor the OBD STATUS for DTC P1078 in the DTC's MENU with the HDS.
Does the screen indicates PASSED?
YES - If the PCM was updated, troubleshooting is complete If the PCM was substituted, replace the original PCM.. Service and Repair If any other Temporary DTCs or DTCs were indicated in step 40, go to the indicated DTC's troubleshooting.
NO - If the screen indicated FAILED, check for poor connections or loose terminals at the IMT actuator and the PCM. If the PCM was updated, substitute a known-good PCM, Initial Inspection and Diagnostic Overview then go to step 39. If the PCM was substituted, go to step 1. If the screen indicates NOT COMPLETED, keep idling until a result comes on.