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Home › Acura › 2003 › MDX Base › Repair and Diagnosis › Engine Performance › System › Engine Performance System Self-Diagnostics › Diagnostic Tests › DTC P1078: Intake Manifold Runner Control Valve Stuck Long

DTC P1078: Intake Manifold Runner Control Valve Stuck Long

CAUTION: When substituting or replacement of PCM is recommended, see PCM REMOVAL & REPLACEMENT  for important precautions.
  1. Turn ignition on. DO NOT start engine. Using Honda PGM Tester or the HDS, do the DTC CLEAR in the CLEAR menu.
  2. Using Honda PGM Tester or the HDS, make sure IMRC SOL is ON in the DATA list. Check IMRC VLV SW in the DATA list. If it is OPEN, problem is intermittent, system is OK at this time. Check for poor connections or loose terminals at intake manifold runner control (IMRC) actuator and PCM connectors. If it is not OPEN, go top next step.
  3. Turn ignition off. Disconnect IMRC actuator 5-pin connector. Go to next step.
  4. Turn ignition on. Measure voltage between ground and IMRC actuator 5-pin connector terminal No. 3 (White/Black wire). If there is about 5 volts, go to next step. If there is not about 5 volts. Go to step  6 .
  5. Turn ignition off. Disconnect PCM harness connector "A". See Figure . Check for continuity between PCM harness connector terminal A28 (Green/Yellow wire) and IMRC actuator 5-pin connector terminal No. 2. If there is continuity, go to step  7 . If there is no continuity, repair open in wire between PCM harness connector terminal A28 and IMRC actuator 5-pin connector terminal No. 2. Go to step  13 .
  6. Turn ignition off. Disconnect PCM harness connector "A". Check for continuity between PCM harness connector terminal A41 (White/Black wire) and IMRC actuator 5-pin connector terminal No. 3. If there is continuity, go to step  15 . If there is no continuity, repair open in wire between PCM harness connector terminal A41 and IMRC actuator 5-pin connector terminal No. 3. Go to step  13 .
  7. Check for continuity between PCM harness connector terminal A9 (White/Blue wire) and IMRC actuator 5-pin connector terminal No. 5. If there is continuity, go to next step. If there is no continuity, repair open in wire between PCM harness connector terminal A9 and IMRC actuator 5-pin connector terminal No. 5. Go to step  13 .
  8. Check for continuity between ground and PCM harness connector terminal A9 (White/Blue wire). If there is continuity, repair short in wire between PCM harness connector terminal A9 and IMRC actuator. Go to step  13 . If there is no continuity, go to next step.
  9. Check for continuity between PCM harness connector terminal A10 (White/Red wire) and IMRC actuator 5-pin connector terminal No. 4. If there is continuity, go to next step. If there is no continuity, repair open in wire between PCM harness connector terminal A10 and IMRC actuator 5-pin connector terminal No. 4. Go to step  13 .
  10. Check for continuity between ground and PCM harness connector terminal A10 (White/Red wire). If there is continuity, repair short in wire between PCM harness connector terminal A10 and IMRC actuator. Go to step  13 . If there is no continuity, go to next step.
  11. Remove the intake manifold runner control valve actuator.
  12. Move the intake manifold runner control valve by hand. If it moves smoothly, replace the IMRC valve actuator. Go to next step. If it does not move smoothly, remove the intake manifold upper cover and repair the stuck valve. If necessary, replace the intake manifold. Go to next step.
  13. Turn ignition on. With the Honda PGM tester or the HDS, do PCM RESET in the CLEAR menu. Go to next step.
  14. Do the PCM idle learn procedure. See PCM IDLE LEARN PROCEDURE  . Using Honda PGM Tester or the HDS, check for Temporary DTCs or DTCs in the DTC menu. If DTC P1078 is set, check for poor connections or loose terminals at IMRC valve actuator. Go to  1 . If any other Temporary DTCs or DTCs are set, troubleshoot those indicated. If Temporary DTCs or DTCs are not set, troubleshooting is done.
  15. Update the PCM if it does not have the latest software, or substitute a known-good PCM. Do the PCM idle learn procedure. See PCM IDLE LEARN PROCEDURE  . Check for Temporary DTCs or DTCs in the DTC menu. If DTC P1078, check for poor connections or loose terminals at IMRC valve actuator and PCM harness connector. Go to  1 . If any other Temporary DTCs or DTCs are set, troubleshoot those indicated. If there are no Temporary DTCs or DTCs set, PCM was updated, troubleshooting is complete. If PCM was substituted, replace original PCM.
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