Ambient Air Temperature Sensor Circuit Low Input
The P0072 code indicates that the Powertrain Control Module (PCM) has detected a voltage signal from the ambient air temperature (AAT) sensor that is lower than the expected range. This sensor measures outside air temperature and is used for HVAC control and other engine management functions. A low input typically means the sensor circuit has a short to ground, a faulty sensor, or a wiring issue.
01. Most Common Causes
- Faulty ambient air temperature sensor
- Short to ground in the sensor circuit
- Damaged wiring or connector
- Corroded terminals
- PCM failure (rare)
02. Symptoms You Will Notice
- Inaccurate outside temperature display
- HVAC system may not function properly
- Check Engine Light illuminated
- Possible hard starting or poor fuel economy
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm the code and check for other related codes.
Step 2: Visually inspect the AAT sensor and its wiring for damage, corrosion, or loose connections.
Step 3: Measure the sensor's resistance and compare to manufacturer specifications (typically 2-10 kΩ at 77°F).
Step 4: Check for voltage at the sensor connector (should be around 5V reference). If low, check for shorts to ground.
Step 5: If sensor and wiring are okay, test the PCM output or replace the 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 work correctly and fuel economy could be slightly affected. It's best to diagnose and repair soon.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150, including parts (sensor $20-$50) and labor (0.5-1 hour).