Staff Answer
Jun 26, 2026 - 08:44 AM
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Code P2078 indicates an "Intake Manifold Tuning Valve Position Sensor/Switch Circuit Range/Performance" fault. This means the engine control module has detected that the tuning valve (which adjusts airflow inside the intake manifold) is not moving to the commanded position.
Common causes include:
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Failed Tuning Valve Actuator: The motor that moves the valve has burnt out.
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Stuck Valve: Carbon buildup or debris is physically preventing the intake manifold tuning valve from rotating.
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Wiring/Connector Faults: Loose or corroded wiring in the actuator circuit.
Quick Steps: Inspect the intake manifold for vacuum leaks or loose electrical connections at the tuning valve actuator. Manually attempt to move the actuator linkage (if accessible) to check for resistance or binding. If the linkage moves freely, test the actuator with a scan tool's "bi-directional control" function to see if it responds; if not, the actuator or sensor requires replacement.
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