P0878
Transmission Fluid Pressure Sensor/Switch "D" Circuit High
- Severity
- High
- Driving
- Drive only to a garage
The signal from transmission fluid pressure sensor or switch "D" is stuck high - usually a short to voltage or a lost earth, though genuinely excessive pressure will also produce it. Excessive line pressure makes shifts violent and puts shock loads through the whole driveline.
Possible causes
- CommonWiring shorted to voltage, or a lost sensor earth
- CommonCorroded transmission case connector, or fluid wicking into it
- CommonFailed pressure sensor or switch
- PossiblePressure control solenoid stuck, producing genuinely high pressure
- PossibleInternal transmission harness failure
- PossibleBlocked return passage holding pressure up
What you might notice
- Very harsh, banging shifts
- Harsh engagement into drive or reverse
- Transmission stuck in one gear
- Several transmission codes together
- Check engine light on
What to check, in order
- Note whether the shifts are actually harsh. If they are, the pressure may genuinely be high and the sensor is telling the truth.
- Check the sensor earth before assuming a shorted signal wire - a lost earth commonly drives a signal high.
- Unplug at the case connector and check whether the high reading persists at the harness.
- Inspect the connector for fluid and corrosion.
- Read all codes - a pressure control solenoid code alongside this one identifies the real cause.
- Very harsh shifts put shock loads through driveshafts and mountings. Do not drive it like this longer than necessary.
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
Transmission
P0800P0801P0802P0803P0804P0805P0806P0807P0808P0809P0810P0811P0812P0813P0814P0815P0816P0817P0818P0819P0820P0821P0822P0823P0824P0825P0826P0827P0828P0829P0830P0831P0832P0833P0834P0835P0836P0837P0838P0839P0840P0841P0842P0843P0844P0845P0846P0847P0848P0849P0850P0851P0852P0853P0854P0855P0856P0857P0858P0859P0860P0861P0862P0863P0864P0865P0866P0867P0868P0869P0870P0871P0872P0873P0874P0875P0876P0877P0878P0879P0880P0881P0882P0883P0884P0885P0886P0887P0888P0889P0890P0891P0892P0893P0894P0895P0896P0897P0898P0899