P0070 – Ambient Air Temperature Sensor Circuit
The P0070 diagnostic trouble code indicates that the Engine Control Module (ECM) has detected a malfunction in the Ambient Air Temperature (AAT) sensor circuit. This sensor measures the outside air temperature and provides data used by the ECM and, on many vehicles, the climate control system.
If the ECM receives an invalid signal or detects an electrical fault in the sensor circuit, it stores the P0070 code and illuminates the Check Engine Light.
Common Symptoms
- Check Engine Light ON
- Incorrect outside temperature display
- Poor air conditioning or climate control performance
- Possible cold start fuel mixture issues on some vehicles
Common Causes
- Faulty ambient air temperature sensor
- Open or shorted wiring
- Loose or corroded connector
- Damaged sensor from road debris or impact
- Rarely, a faulty ECM
Basic Diagnosis
Inspect the ambient air temperature sensor, usually located behind the front grille or bumper. Check the wiring and connector for damage or corrosion, verify the sensor reference voltage and ground, and compare the sensor reading on a scan tool with the actual outside temperature. Replace the sensor if it is out of specification.