Ambient Air Temperature Sensor Range/Performance
The P0071 code indicates that the Engine Control Module (ECM) has detected an ambient air temperature (AAT) sensor signal that is out of the expected range or performing erratically. The AAT sensor measures outside air temperature and is used for HVAC control and certain engine management functions. A faulty sensor, wiring issues, or a short circuit can trigger this code.
01. Most Common Causes
- Faulty ambient air temperature sensor
- Open or shorted wiring in the sensor circuit
- Poor electrical connection at the sensor
- Corrosion or damage to the sensor connector
02. Symptoms You Will Notice
- Inaccurate outside temperature display
- HVAC system not working properly (e.g., incorrect auto climate control)
- Check Engine Light illuminated
- Possible hard starting or poor fuel economy (rare)
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to verify the code and check for related codes.
Step 2: Visually inspect the AAT sensor and its wiring for damage, corrosion, or loose connections.
Step 3: Compare the sensor's resistance reading to the manufacturer's specifications at known temperatures.
Step 4: Test the sensor circuit for continuity and shorts to ground or power.
Step 5: If all checks pass, replace the ambient air temperature sensor.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, it is generally safe to drive, but the HVAC system may not function correctly, and the check engine light will remain on. It is best to diagnose and repair soon to avoid potential drivability issues.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150, including parts and labor. The sensor itself is inexpensive (around $20-$50), and labor is minimal (0.5-1 hour).