What Does P0073 Mean?
The ECM has detected that the ambient air temperature (AAT) sensor circuit voltage is above the maximum expected threshold, indicating a high input condition. For a typical NTC thermistor, high voltage corresponds to very low resistance, which the ECM interprets as an extremely high temperature. This usually indicates a short to ground in the sensor or its wiring. The driver will see an abnormally high outside temperature reading displayed and the check engine light.
Common Causes
35%
Shorted AAT sensor element (internal short to ground)
28%
Wiring short to ground — sensor signal wire touching chassis or ground wire
20%
Water intrusion in the sensor connector creating a low-resistance path to ground
12%
Physical damage to sensor or wiring causing signal wire to contact vehicle body
5%
ECM signal circuit fault or wrong sensor installed
Diagnostic Steps
1
Check the AAT PID reading — an abnormally high temperature value (e.g., 250°F+) with a high circuit voltage confirms a short to ground condition in the NTC sensor circuit.
2
Disconnect the AAT sensor connector. If the PID reading changes to -40°F (open circuit), the short is inside the sensor itself. If it stays high, the short is in the wiring.
3
Measure resistance from each sensor connector wire to chassis ground (sensor disconnected). The signal wire should show infinite resistance (OL) to ground. A low reading indicates a wire-to-ground short.
4
Inspect the sensor connector for water, salt, or corrosion. The sensor's location behind the bumper makes it extremely vulnerable to road splash. Dry the connector and apply dielectric grease.
5
Trace the sensor wiring from the bumper through any grommets and connectors to the engine compartment. Look for bare wire touching the vehicle body, especially where the harness passes through sheet metal.
Estimated Repair Cost
$30 - $200
Parts + labor, varies by vehicle and location
The ECM has detected that the ambient air temperature (AAT) sensor circuit voltage is above the maximum expected threshold, indicating a high input condition. For a typical NTC thermistor, high voltage corresponds to very low resistance, which the ECM interprets as an extremely high temperature. Thi...
The most common cause of P0073 (Ambient Air Temperature Sensor Circuit High Input) is: Shorted AAT sensor element (internal short to ground)
Typical repair costs for P0073 range from $30 to $200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive. The ECM will use a default substitute value. Outside temperature display will be incorrect. Minor impact on fuel mixture calculations and A/C operation. Will fail emissions inspection. Low priority repair.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0073 to identify the root cause.
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Quick Info
Category
Powertrain
System
Engine Management / Climate Control
Difficulty
Type
Generic (SAE)
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