P0073 – Ambient Air Temperature Sensor Circuit High
The P0073 diagnostic trouble code indicates that the Engine Control Module (ECM) has detected a higher-than-expected voltage signal from the Ambient Air Temperature (AAT) sensor circuit.
The AAT sensor is typically a Negative Temperature Coefficient (NTC) thermistor. A high circuit voltage usually indicates an extremely low temperature reading or an open circuit in the sensor wiring. When this condition is detected, the ECM stores the P0073 code and illuminates the Check Engine Light.
Common Symptoms
- Check Engine Light ON
- Incorrect outside temperature display
- Automatic climate control may operate incorrectly
- Possible air conditioning performance issues
Common Causes
- Open circuit in the sensor wiring
- Faulty ambient air temperature sensor
- Disconnected or corroded electrical connector
- Damaged wiring harness
- Rarely, a faulty ECM
Basic Diagnosis
Inspect the sensor connector and wiring for damage or loose connections, verify the reference voltage and ground, compare the sensor reading on a scan tool with the actual outside temperature, and measure the sensor resistance according to the manufacturer's specifications.