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

P0074 Ambient Air Temperature Sensor Circuit A Intermittent/Erratic

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. P0074 is set when the signal jumps or is noisy, i.e. changes faster than a real temperature can, which typically points to a loose contact.

Likely causes

Loose contact or corrosion at the connector
Wire broken inside the harness
Sensor faulty

Symptoms

  • Outside temperature display jumps
  • 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

P0070P0071P0072P0073

References: law.cornell.edu, gsi.ext.gm.com, en.wikipedia.org.