P0850
Park/Neutral Switch Input Circuit
- Severity
- High
- Driving
- Drivable — book it in
A fault in the circuit for the park/neutral switch, which tells the module the transmission is in park or neutral, which is what permits the engine to be started. When the module cannot trust this input, starting behaviour becomes unpredictable - and if the interlock it feeds stops working, the engine can crank with a gear selected.
Possible causes
- CommonFailed or misadjusted switch, often part of the transmission range sensor
- CommonWorn selector linkage, so the switch is never moved fully
- CommonCorroded connector at the transmission
- PossibleWiring damage under the vehicle
- PossibleAftermarket alarm or remote start spliced into the circuit
What you might notice
- Engine will not crank in park, but will in neutral or vice versa
- Engine cranks with a gear selected - it must not
- Reversing lamps wrong
- Gear display wrong
- Check engine light on
What to check, in order
- Test whether the engine cranks with a gear selected - handbrake on, wheels chocked, nobody in front of or behind the car. If it cranks in gear, stop using the vehicle until it is fixed.
- Check the switch or range sensor adjustment. Adjustment is often the entire repair.
- Watch the selected gear on the live data screen through the full selector travel.
- Check the selector cable and linkage for wear.
- Inspect the connector at the transmission for corrosion.
- Ask whether an aftermarket alarm or remote start has been fitted.
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