P0073
UniversalAmbient Air Temperature Sensor Circuit High Input
Medium SeverityThe vehicle's computer detects a voltage signal from the Ambient Air Temperature (AAT) sensor that is higher than expected, indicating an open circuit or a short to voltage. This can lead to incorrect calculations for fuel delivery and impact engine performance and fuel efficiency.
⚠️ Before You Begin (Safety First)
Always disconnect the battery before performing any electrical work. Allow the engine to cool down completely before working in the engine bay to avoid burns from hot components.
Common Symptoms
- Check Engine Light illuminated
- Poor fuel economy
- Rough idling or decreased engine performance (less common)
- Incorrect or absent outside temperature display on the dashboard
- Problems with automatic climate control operation
Common Causes
- Faulty Ambient Air Temperature (AAT) sensor
- Open circuit in the AAT sensor wiring (e.g., broken wire)
- Short to voltage in the AAT sensor circuit
- Corroded or loose electrical connections at the sensor or Engine Control Module (ECM)
- Faulty Engine Control Module (ECM) (rare)
Frequently reported on: General/Universal
Diagnostic Steps
- Locate the Ambient Air Temperature sensor, often found behind the front grille, bumper, or sometimes in the side mirror.
- Visually inspect the AAT sensor and its electrical connector and wiring for any signs of damage, fraying, corrosion, or loose connections.
- Using a multimeter, test the resistance of the AAT sensor. Compare the readings to the manufacturer's specifications for various temperatures.
- With the ignition on (engine off), use a multimeter to check for a reference voltage (typically 5V) at the sensor's connector and a good ground connection.
- Repair or replace any damaged wiring or corroded connectors. Ensure all connections are secure.
- If the sensor fails resistance tests or shows no proper voltage/ground at the connector, replace the Ambient Air Temperature sensor.
- Clear the P0073 diagnostic trouble code from the ECM using an OBD-II scanner and test drive the vehicle to confirm the repair.
👨🔧 When to Call a Professional
If a thorough diagnosis of the Ambient Air Temperature sensor and its circuit wiring confirms they are functioning correctly, the issue might stem from a faulty Engine Control Module (ECM). In such complex cases, it is best to consult a professional automotive technician.
Commonly Asked Questions
What does P0073 'Ambient Air Temperature Sensor Circuit High Input' specifically mean?
This code indicates that the vehicle's engine control module (ECM) is receiving an abnormally high voltage signal from the ambient air temperature sensor. A high voltage typically means the circuit is open or shorted to a voltage source, leading the ECM to interpret the outside temperature as extremely low or a default high resistance value.
Can I continue driving my car with a P0073 code?
While it's generally safe to drive with a P0073 code, it's not recommended for extended periods. The incorrect temperature readings can affect fuel efficiency, engine performance, automatic climate control, and emissions. It's best to diagnose and repair the issue promptly.
Is the Ambient Air Temperature (AAT) sensor the same as the Intake Air Temperature (IAT) sensor?
No, they are different sensors with different functions. The AAT sensor measures the outside ambient air temperature, primarily for dashboard display and some environmental controls. The IAT sensor measures the temperature of the air entering the engine's intake manifold, which is crucial for precise fuel mixture calculations.
How do I test the Ambient Air Temperature sensor to confirm it's faulty?
You can test the sensor's resistance using a multimeter. Disconnect the sensor and measure the resistance across its terminals. Compare this reading to the resistance-to-temperature chart provided in your vehicle's service manual. An open circuit (infinite resistance) or a reading far from specifications indicates a faulty sensor.
What if replacing the AAT sensor doesn't clear the P0073 code?
If a new sensor doesn't resolve the code, the problem likely lies within the wiring harness connecting the sensor to the ECM. You'll need to inspect the wiring for open circuits, shorts to voltage, or corroded connections. In rare cases, the ECM itself could be faulty, requiring professional diagnosis.