Ambient Air Temperature Sensor Range/Performance
The P0071 code indicates that the Engine Control Module (ECM) has detected an ambient air temperature sensor reading that is outside the expected range or not performing correctly. This sensor measures the outside air temperature and is used for various systems, including HVAC and engine management. The ECM compares the sensor's voltage signal to predefined thresholds; if the signal is erratic, out of range, or inconsistent with other sensor data (like intake air temperature), the code sets. Common causes include a faulty sensor, wiring issues, or corrosion at the connector.
1. Most Common Causes
- Faulty ambient air temperature sensor
- Damaged or corroded wiring/connector
- Short circuit in the sensor circuit
- ECM software or hardware issue (rare)
2. Symptoms You Will Notice
- Inaccurate outside temperature display
- HVAC system not working properly (e.g., incorrect auto climate control)
- Check Engine Light illuminated
- Possible poor fuel economy or engine performance issues
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for other related codes.
Step 2: Visually inspect the ambient air temperature sensor and its wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor's resistance with a multimeter and compare to manufacturer specifications.
Step 4: Check the voltage signal at the sensor connector with the ignition on; should be around 5V reference and a varying signal based on temperature.
Step 5: If sensor and wiring are okay, test the ECM's ability to read the sensor by monitoring live data with a scan tool.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
Yes, it is generally safe to drive, but the HVAC system may not work correctly, and fuel economy could be slightly affected. However, if the sensor fails completely, it may cause the engine to run poorly in extreme temperatures.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150, including parts and labor. The sensor itself is usually inexpensive ($20-$50), and labor is minimal (0.5-1 hour).
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.