Ambient Air Temperature Sensor Circuit Low
Diagnostic trouble code P0072 indicates that the Powertrain Control Module (PCM) has detected an abnormally low voltage signal from the Ambient Air Temperature (AAT) sensor circuit. This low voltage typically signifies a short to ground, causing the computer to register an inaccurately high outside air temperature.
This code is not a safety hazard and will not leave you stranded. However, it should be addressed to restore proper automatic climate control operation and optimal fuel efficiency.
Common symptoms
- Illuminated Check Engine Light
- Inaccurate outside temperature reading on the dashboard display
- Air conditioning system fails to cool or compressor does not engage
- Automatic climate control system functions erratically
- Slight decrease in fuel economy due to incorrect air density calculations
Likely causes
- Faulty Ambient Air Temperature (AAT) sensor
- Short to ground in the AAT sensor wiring harness
- Corroded, damaged, or loose electrical connector at the sensor
- Sensor covered in debris or improperly mounted
- Faulty Powertrain Control Module (PCM) or climate control module (rare)
What to check before replacing parts
Visually inspect the AAT sensor, usually located behind the front grille, and its wiring harness.
Look for: Look for physical damage to the sensor, frayed wires, or a corroded connector that could cause a short to ground.
Use a scan tool to monitor the AAT sensor data PID.
Look for: Check if the temperature reading is unrealistically high (e.g., maxed out) compared to the actual outside temperature, which confirms the low voltage/short condition.
Disconnect the AAT sensor and observe the scan tool data or measure the connector voltage.
Look for: If the scan tool reading drops to an extreme cold value (or the connector shows a 5V reference), the wiring is likely good and the sensor itself is internally shorted.
Measure the internal resistance of the AAT sensor using a multimeter.
Look for: Compare the resistance reading to the manufacturer's temperature-resistance chart; a reading of near zero ohms indicates a shorted sensor.
Test the signal wire for a short to ground between the sensor connector and the PCM.
Look for: With both ends disconnected, continuity between the signal wire and chassis ground indicates a short in the wiring harness that must be repaired.
This page explains the generic P0072 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
Gear guide: Best OBD2 ScannersRead this code yourself next time — from $20 Bluetooth dongles to bidirectional scan tools.Rather have a pro handle it? Find a vetted local mechanic.