P0845
Transmission Fluid Pressure Sensor/Switch "B" Circuit
- Severity
- High
- Driving
- Drive only to a garage
A fault in the circuit for transmission fluid pressure sensor or switch "B". Depending on the vehicle this is either a switch that reports whether pressure is present in one hydraulic circuit, or a sensor that reports how much. Either way, the module uses it to confirm that the clutch it just commanded actually received pressure - so without it, the module cannot verify its own shifts and will fall back to a failsafe.
Possible causes
- CommonFailed pressure sensor or switch
- CommonCorroded transmission case connector, or fluid wicking into it
- CommonInternal transmission harness failure
- PossibleWiring damage between the transmission and the module
- PossibleLow fluid level or genuinely low pressure
- PossibleDebris blocking the pressure passage to the sensor
What you might notice
- Transmission stuck in one gear
- Harsh or delayed shifts
- Slipping
- Several transmission codes stored together
- Check engine light on
What to check, in order
- Check the fluid level and condition first - low fluid produces genuinely low pressure and this code with a perfectly good sensor.
- Read all transmission codes together. Several pressure sensor codes at once point at the case connector, the internal harness or genuinely low line pressure, not at several failed sensors.
- Inspect the case connector for fluid ingress and corroded pins.
- Watch the reported pressures on the live data screen against the specification for each gear.
- Expect these sensors to be inside the transmission on most vehicles. Eliminate the external wiring and the case connector before dropping the pan.
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