P1078

DTC P1078: IMRC System Malfunction (High rpm)

1. Reset the ECM/PCM.
2. Start the engine, and hold it at 3,000 rpm with no load (in Park or neutral) until the radiator fan comes on.
3. Raise the engine speed to 5,000 rpm.

Is DTC P1078 indicated?

YES - Go to step 4.

NO - Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the Intake Manifold Runner Control (IMRC) solenoid valve and at the ECM/PCM.

4. Disconnect the vacuum hose (A) from the Intake Manifold Runner Control (IMRC) actuator (B), and connect a vacuum pump to the hose.




5. Raise the engine speed to 5,000 rpm.

Is there vacuum?

YES - Go to step 6.

NO - Go to step 15.

6. Turn the ignition switch OFF.
7. Disconnect the IMRC solenoid valve 2P connector.
8. Start the engine.




9. Raise the engine speed to 5,000 rpm, then measure voltage between IMRC solenoid valve 2P connector terminal No.1 and No.2.

Is there battery voltage?

YES - Replace the IMRC solenoid valve.

NO - Go to step 10.




10. Measure voltage between IMRC solenoid valve 2P connector terminal No.1 and body ground.

Is there battery voltage?

YES - Go to step 11.

NO - Check the No.4 ACG (10A) fuse in the underdash fuse/relay box. If the fuse OK, repair open in the wire between the IMRC solenoid valve and No. 4ACG (10A) fuse.

11. Turn the ignition switch OFF.
12. Disconnect ECM/PCM connector B (24P).




13. Connect IMRC solenoid valve 2P connector terminal No.2 to body ground with a jumper wire.




14. Check for continuity between ECM/PCM connector terminal B22 and body ground.

Is there continuity?

YES - Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM.

NO - Repair open in the wire between the ECM/PCM (B22) and the IMRC solenoid valve.

15. Turn the ignition switch OFF.




16. Connect the vacuum pump to the IMRC actuator (A), then apply vacuum.

Does the IMRC actuator hold vacuum?

YES - Go to step 17.

NO - Replace the IMRC valve assembly.

17. Disconnect the IMRC valve position sensor 3P connector.




18. At the sensor side, measure resistance between the IMRC valve position sensor 3P connector terminals No.2 and No.3 while applying vacuum to the IMRC actuator.

Is there about 9.5 kOhm?

YES - Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM.

NO - Replace the IMRC valve assembly.