Faulty or drifting ambient air temperature sensor; Damaged, corroded or loose sensor connector or wiring, including high resistance; Sensor placed where it is heated by radiator, engine bay heat or sun, or blocked by debris or damage after front-end work; Sensor reading shared over the network from another module being wrong or delayed; Related intake air or coolant temperature sensor giving a faulty reading that the unit uses for comparison; Fault in the control unit or the module that reads the sensor.

P0071

Ambient Air Temperature Sensor Circuit A Range/Performance.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
0: AreaFuel and air metering, auxiliary emission controls
71: FaultThe specific fault in that area

What it means

P0071 is the generic code for an ambient air temperature sensor circuit range or performance fault. The control unit has compared the reading from the outside air temperature sensor with other inputs, such as intake air temperature, coolant temperature after a long soak, or a model of expected values, and found it implausible. It may also see a reading that is stuck or changes too slowly or too quickly for the conditions.

Symptoms

Engine warning light on
Outside temperature display on the dashboard reading wrongly or stuck
Climate control or automatic air conditioning behaving oddly
Slightly rough or slow cold start on some vehicles
Often no obvious drivability symptoms at all

Possible causes

Faulty or drifting ambient air temperature sensorlikely
Damaged, corroded or loose sensor connector or wiring, including high resistancelikely
Sensor placed where it is heated by radiator, engine bay heat or sun, or blocked by debris or damage after front-end workpossible
Sensor reading shared over the network from another module being wrong or delayedpossible
Related intake air or coolant temperature sensor giving a faulty reading that the unit uses for comparisonpossible
Fault in the control unit or the module that reads the sensorrare

How to diagnose

Read the stored codes and freeze frame data, and note whether other temperature or sensor circuit codes are present
Check the ambient temperature reading in live data on a cold car that has been standing for several hours, and compare it with intake air and coolant temperature, which should all be close
Inspect the sensor, its mounting position and the surrounding area for damage, dirt, water ingress or signs of recent front-end repair
Check the connector and wiring for corrosion, bent pins, chafing and poor terminal tension
Compare the live reading with a known accurate thermometer, then warm the sensor gently and confirm the reading rises and falls smoothly
Measure the sensor resistance and the supply and ground at the connector against the manufacturer specification for your model
Check which module reads the sensor and how the value is sent to the engine control unit, as this varies by make and model

How to fix

Replace the ambient air temperature sensor if it fails the resistance or response checks
Repair or replace damaged wiring and clean or renew corroded connector terminals
Refit or reposition the sensor to its correct location and clear any blockage or damage around it
Replace a faulty intake air or coolant temperature sensor if that is the cause of the mismatch
Repair the network or module fault if the sensor value is being passed on incorrectly, following the manufacturer procedure
Clear the code and road test to confirm it does not return

Can I keep driving?

Low severity

The car can normally be driven as usual, as this fault rarely affects safety or causes damage. Book it in at your convenience, as the engine warning light will stay on and could hide a new fault.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.