P1078
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. Hold the engine speed above 4,000 rpm.
4. Make sure the IMT VALVE CMD is OPEN in the DATA LIST with the HDS.
5. Check the IMT VALVE SW in the DATA LIST with the HDS.
Is CLOSED indicated?
YES - Go to step 6.
NO - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the IMT actuator and the 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.
Is there about 5 V?
YES - Go to step 10.
NO - Repair open in the wire between the PCM (C14) and the IMT actuator, then go to step 27.
10. Measure voltage between IMT actuator 5P connector terminal No. 3 and body ground.
Is there about 5 V?
YES - Go to step 11.
NO - Go to step 16.
11. Turn the ignition switch OFF.
12. Jump the SCS line with the HDS.
13. Disconnect PCM connector C (22P).
14. Connect IMT actuator 5P connector terminal No. 2 to body ground with a jumper wire.
15. Check for continuity between PCM connector terminal C12 and body ground.
Is there continuity?
YES - Go to step 19.
NO - Repair open in the wire between the PCM (C12) and the IMT actuator, then go to step 27.
16. Disconnect PCM connector B (24P).
17. Connect IMT actuator 5P connector terminal No. 3 to body ground with a jumper wire.
18. Check for continuity between PCM connector terminal B11 and body ground.
Is there continuity?
YES - Go to step 34.
NO - Repair open in the wire between the PCM (B11) and the IMT actuator, then go to step 27.
19. Check for continuity between PCM connector terminal B4 and body ground.
Is there continuity?
YES - Repair short in the wire between the PCM (B4) and the IMT actuator, then go to step 27.
NO - Go to step 20.
20. Connect IMT actuator 5P connector terminal No. 5 to body ground with a jumper wire.
21. Check for continuity between PCM connector terminal B4 and body ground.
Is there continuity?
YES - Go to step 22.
NO - Repair open in the wire between the PCM (B4) and the IMT actuator, then go to step 27.
22. Check for continuity between PCM connector terminal B3 and body ground.
Is there continuity?
YES - Repair short in the wire between the PCM (B3) and the IMT actuator, then go to step 27.
NO - Go to step 23.
23. Connect IMT actuator 5P connector terminal No. 4 to body ground with a jumper wire.
24. Check for continuity between PCM connector terminal B3 and body ground.
Is there continuity?
YES - Go to step 25.
NO - Repair open in the wire between the PCM (B3) and the IMT actuator, go to step 27.
25. Remove the IMT actuator.
26. Move the IMT valve by hand.
Does it move smoothly?
YES - Substitute a known-good IMT actuator, then go to step 27 and recheck. If DTC P1078 is not indicated, replace the IMT actuator, then go to step 27. If DTC P1078 is indicated, then go to step 34.
NO - Remove the intake manifold upper cover, and repair the stuck valve. If necessary, replace the intake manifold, then go to step 27.
27. Reconnect all connectors.
28. Turn the ignition switch ON (II).
29. Reset the PCM with the HDS.
30. Do the PCM idle learn procedure.
31. Start the engine. Hold the engine speed at 4,000 rpm for 10 seconds, then let it idle.
32. 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 PCM, then go to step 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.
NO - Go to step 33.
33. Monitor the OBD STATUS for DTC P1077 in the DTCs MENU with the HDS.
Does the screen indicate PASSED?
YES - Troubleshooting is complete.
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, go to step 30 and recheck.
34. Update the PCM if it does not have the latest software, or substitute a known-good PCM.
35. Start the engine. Hold the engine speed at 4,000 rpm for 10 seconds, then let it idle.
36. 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 PCM, then go to step 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.
NO - If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM.