P0072 – Ambient Air Temperature Sensor Circuit Low
The P0072 diagnostic trouble code indicates that the Engine Control Module (ECM) has detected a lower-than-expected voltage signal from the Ambient Air Temperature (AAT) sensor circuit.
Since the AAT sensor is typically a Negative Temperature Coefficient (NTC) thermistor, a low circuit voltage usually indicates an extremely high temperature reading or a short to ground in the sensor circuit. When this condition is detected, the ECM stores the P0072 code and illuminates the Check Engine Light.
Common Symptoms
- Check Engine Light ON
- Incorrect outside temperature display
- Automatic climate control may not operate correctly
- Possible A/C performance issues on some vehicles
Common Causes
- Short to ground in the sensor circuit
- Faulty ambient air temperature sensor
- Damaged or pinched wiring
- Corroded or loose electrical connector
- Rarely, a faulty ECM
Basic Diagnosis
Inspect the sensor and wiring for damage, check the connector for corrosion, verify the reference voltage and ground, monitor the sensor value using a scan tool, and measure the sensor resistance according to the manufacturer's specifications.
Diagnostic Note: The AAT sensor is usually a two-wire NTC thermistor. Sensor voltage, resistance values, and circuit design vary by manufacturer. Always refer to the factory wiring diagram and service manual before performing electrical tests.