P2078
Intake Manifold Tuning (IMT) Valve Position Sensor/Switch Circuit High
- Severity
- Medium
- Driving
- Drivable — book it in
The intake manifold tuning valve position signal is reading high - typically shorted to voltage or with a lost earth.
Possible causes
- CommonFailed runner position sensor
- CommonCarbon seizing the flaps, so the sensor correctly reports they are not moving
- CommonCorroded connector or damaged wiring
- CommonBroken linkage between the actuator and the sensor
- PossibleLoss of reference voltage or earth
What you might notice
- Loss of low-speed torque or flat top-end power
- Rough idle
- Hesitation
- Worse fuel economy
- Smoke on a diesel
- Check engine light on
What to check, in order
- Check the valve moves freely before condemning the sensor.
- Check the vacuum hoses first on a vacuum-operated system - a split or disconnected hose is the most common cause and the cheapest to fix.
- Check the flaps and linkage move freely. Carbon seizing them is very common on a diesel used for short journeys, and cleaning is often the whole repair.
- Watch commanded against actual runner position on the live data screen through a sweep.
- Inspect the connector for corrosion and the actuator for damage.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Fuel, air metering and auxiliary emission controls
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