The P0071 code indicates that the Engine Control Module (ECM) has detected a signal from the ambient air temperature sensor that is outside the expected operating range or is illogical. This typically means the sensor is reporting a temperature that is physically impossible or inconsistent with other vehicle data.
The sensor's internal thermistor has failed or drifted out of its calibrated resistance range.
Exposed wiring to the elements can lead to corrosion, fraying, or short circuits, altering the signal voltage.
Corroded or loose connector pins at the sensor or the ECM harness create intermittent high resistance.
The sensor is positioned too close to a heat source or is blocked, causing readings that the ECM deems unrealistic.
The engine control module is incorrectly processing the sensor signal or has an internal circuit failure.
No, the vehicle will typically remain drivable, although HVAC performance and fuel efficiency may be slightly impacted.
Yes, many vehicles use the ambient air temperature reading to determine when to engage the A/C compressor or adjust the blend doors.
No. It is extremely rare for the PCM to be the cause of P0071; you should first re-verify the wiring integrity and connector tension.