The outside air temperature reading is implausible. Mostly a comfort and economy nuisance, but on some cars it upsets fuelling and auto climate control.
P0071 — also written POO71, P 0071, 0071 — is the OBD-II code for ambient air temperature sensor range/performance. Same code, same fix: this page covers every spelling of it.
P0071 is a sensors fault code, typically costing £30–£160 to put right in a UK garage.
What causes P0071?
- Failed ambient sensor behind the front bumper
- Sensor caked in road salt and grime
- Wiring damage from a minor front-end knock
How P0071 is fixed
- Clean or replace the ambient sensor
- Repair wiring behind the bumper
P0071 repair cost in the UK
Most P0071 repairs land between £30–£160 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 P0071?
Yes.
Urgency: low.
What P0071 is telling you
The ECU runs continuous plausibility checks against what a good engine should be doing. When a reading strays outside that model for long enough, this code is stored and the light comes on.
On P0071 specifically — ambient air temperature sensor range/performance — 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 P0071 is diagnosed properly
Each of the known causes is ruled in or out in cost order, cheapest and most likely first. On P0071 that means working through them like this:
- Failed ambient sensor behind the front bumper — compared against live data and a known-good reference before it is condemned — a sensor reading the wrong thing accurately is a different fault from a dead one.
- Sensor caked in road salt and grime — compared against live data and a known-good reference before it is condemned — a sensor reading the wrong thing accurately is a different fault from a dead one.
- Wiring damage from a minor front-end knock — checked with the loom flexed and the engine warm, because a wiring fault that is intermittent when cold shows itself under heat and vibration.
An hour of diagnostic time on P0071 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 P0071
- Clean or replace the ambient sensor
- Repair wiring behind the bumper
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 P0071 is ignored
Low urgency means there is time to book it properly rather than pay emergency rates — not that it can be left indefinitely.
For reference, P0071 typically lands at £30–£160 all-in at an independent garage in the UK — main-dealer quotes for the same job usually sit above that.
Getting P0071 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 P0071 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.