AAT Ambient Air Temperature (AAT) Sensor

Ambient Air Temperature (AAT) Sensor

The Ambient Air Temperature (AAT) Sensor measures the temperature of the outside air and sends this information to the Engine Control Module (ECM) and, on many vehicles, the Heating, Ventilation, and Air Conditioning (HVAC) control module. The sensor helps improve climate control operation and, in some vehicles, assists the ECM in engine management during certain operating conditions.

Common Location

• Behind the front grille
• Behind the front bumper cover
• Near the radiator support, away from engine heat

How It Works

The AAT sensor is a thermistor whose resistance changes with outside air temperature. As the temperature changes, the ECM receives a different voltage signal and calculates the ambient air temperature.

Symptoms of a Faulty AAT Sensor

• Incorrect outside temperature display
• Poor automatic climate control performance
• Check Engine Light (on some vehicles)
• DTCs such as P0070, P0071, P0072, or P0073

Common Causes of Failure

• Failed ambient air temperature sensor
• Damaged or corroded wiring
• Loose electrical connector
• Impact damage from road debris

Basic Diagnosis

Inspect the sensor and connector for physical damage, compare the scan tool reading with the actual outside temperature, verify the reference voltage and ground, and measure the sensor resistance according to the manufacturer's specifications.

Related Diagnostic Trouble Codes

• P0070 – Ambient Air Temperature Sensor Circuit
• P0071 – Ambient Air Temperature Sensor Range/Performance
• P0072 – Ambient Air Temperature Sensor Circuit Low
• P0073 – Ambient Air Temperature Sensor Circuit High

Diagnostic Note: The AAT sensor is typically a two-wire Negative Temperature Coefficient (NTC) thermistor. Sensor location, wiring, voltage values, and resistance specifications vary by manufacturer. Always consult the factory service manual and wiring diagram before testing.