Powertrain, generic · Fuel and air metering, auxiliary emission controls

P0071 Ambient Air Temperature Sensor Circuit A Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

The ambient air temperature sensor A is an NTC thermistor whose resistance falls as temperature rises. Its value is used by the climate control, the outside temperature display and the engine control module, which needs it to enable other diagnostics and to correct its maps. Depending on the vehicle the engine control module reads the sensor directly, or the instrument cluster or another module sends the value over the data bus; some vehicles have no sensor and estimate ambient temperature from intake air temperature. P0071 is a plausibility check: after a long standstill (several hours) ambient, intake air and coolant temperatures should be close together. If the ambient reading deviates by more than a threshold at the next start, the code is set; an engine block heater or strong sunshine are excluded where the system can detect them.

Likely causes

Sensor drifting
Sensor mounted in a heat-affected spot, e.g. after a repair
Actually the comparison sensor (intake air or coolant) is faulty
Contact resistance at the connector

Symptoms

  • Wrong or missing outside temperature display
  • Climate control regulates incorrectly
  • Check engine light on (manufacturer-dependent)
  • Other monitors may not complete

Repair estimate

DifficultyEasyDIY possible
Parts and labour€40–200
Time0.3–1 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

ambient air temperature sensorambient air temperature sensor wiringinstrument cluster

Related codes

P0070P0072P0073P009AP011E

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov.