Ambient Air Temperature Sensor Circuit
The Powertrain Control Module (PCM) uses the Ambient Air Temperature (AAT) sensor to monitor the outside air temperature, which helps optimize fuel delivery and climate control operation. Code P0070 is set when the PCM detects an electrical malfunction, such as an open or short, within the AAT sensor circuit.
This code does not typically affect the vehicle's drivability or safety. However, it should be addressed to restore proper automatic climate control function and optimal fuel economy.
Common symptoms
- Illuminated Check Engine Light
- Inaccurate outside temperature reading on the instrument cluster
- Automatic climate control (A/C) system blowing warm air or functioning erratically
- Slight decrease in fuel economy
- Cooling fans running constantly or at inappropriate times
Likely causes
- Faulty Ambient Air Temperature (AAT) sensor
- Damaged, corroded, or loose wiring connector at the AAT sensor
- Physical damage to the sensor from road debris (often located behind the front grille)
- Short or open circuit in the AAT sensor wiring harness
- Faulty Powertrain Control Module (PCM) or climate control module (rare)
What to check before replacing parts
Visually inspect the AAT sensor and its connector (usually located behind the front grille).
Look for: Look for physical damage to the sensor, broken wires, or corrosion inside the connector pins.
Check the outside temperature display on the dashboard.
Look for: If the display shows an extreme temperature (like -40°F or 140°F), it strongly indicates an open or shorted circuit.
Use a scan tool to monitor the AAT sensor live data.
Look for: Compare the AAT reading to the actual outside temperature; a reading that is stuck or wildly inaccurate confirms a circuit or sensor fault.
Disconnect the AAT sensor and test the reference voltage and ground at the connector using a multimeter.
Look for: You should typically see a 5-volt reference signal and a good ground. If either is missing, the wiring harness or module is at fault.
Measure the resistance of the AAT sensor itself using a multimeter.
Look for: Compare the resistance value to the manufacturer's temperature-resistance chart. If the resistance is out of specification or shows an open circuit (OL), the sensor is defective.
This page explains the generic P0070 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.
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