The neutral or park switch signal is wrong. The usual complaint is a car that will not crank, or that cranks in gear when it should not.
P0850 — also written PO85O, P 0850, 0850 — is the OBD-II code for park/neutral switch input circuit. Same code, same fix: this page covers every spelling of it.
P0850 is a transmission fault code, typically costing £90–£420 to put right in a UK garage.
What causes P0850?
- Failed neutral safety or inhibitor switch
- Misadjusted selector linkage
- Corroded connector at the gearbox
- Worn selector cable
How P0850 is fixed
- Adjust or replace the inhibitor switch
- Set the selector cable correctly
- Repair the connector
P0850 repair cost in the UK
Most P0850 repairs land between £90–£420 including parts and labour. The spread is wide because the cheap fix (a sensor, a hose, a leak) and the expensive fix (a major component) throw the same code — which is why a proper diagnosis before parts are bought saves the most money.
Can you drive with P0850?
Yes, though it may refuse to start until the selector is jiggled.
Urgency: medium.
What P0850 is telling you
Transmission codes come from the gearbox control unit comparing commanded gear, clutch or solenoid state against the speeds its sensors report. A mismatch triggers a protection strategy, which is what the driver feels as limp mode or a locked gear.
On P0850 specifically — park/neutral switch input circuit — the stored code records the moment that check failed, not the moment the part gave up. That gap is why two cars with the same code can need completely different repairs.
How P0850 is diagnosed properly
Each of the known causes is ruled in or out in cost order, cheapest and most likely first. On P0850 that means working through them like this:
- Failed neutral safety or inhibitor switch — confirmed with live data before any part is bought.
- Misadjusted selector linkage — confirmed with live data before any part is bought.
- Corroded connector at the gearbox — opened, inspected for green corrosion and spread pins, and back-probed rather than unplugged, so the reading is taken with the circuit live.
- Worn selector cable — confirmed with live data before any part is bought.
An hour of diagnostic time on P0850 routinely saves more than it costs, because the alternative is buying the most expensive part on that list and hoping.
The repairs that actually clear P0850
- Adjust or replace the inhibitor switch
- Set the selector cable correctly
- Repair the connector
After the repair the code is cleared and the car is driven until the relevant readiness monitor completes, rather than handed back as soon as the light goes out. A code that has only been erased will come straight back on the next drive cycle.
What happens if P0850 is ignored
The car will usually keep going, but the fault will not clear itself and the related monitors stay incomplete — which matters if an MOT is due, because a car that has not finished its emissions self-tests can be refused.
For reference, P0850 typically lands at £90–£420 all-in at an independent garage in the UK — main-dealer quotes for the same job usually sit above that.
Getting P0850 looked at
Bob's Mechanical Repairs is an independent garage in Birnam, Dunkeld, Perthshire, with 32 years of Bob's experience on the tools. If P0850 is showing on your car, bring the scan results with you — we will read the live data ourselves, tell you which of the causes above it actually is, and price the repair before any work starts.