P0073 is one of the most prevalent OBD2 trouble codes. In layman’s terms, it indicates that there is an issue with the ambient air sensor.
The ambient air temperature sensor (or AAT for short) is responsible for monitoring outside air temperature and regulating your vehicle’s automatic climate control system. It doesn’t affect the way your car runs or drives at all.
While P0073 is a generic code, repair steps will vary depending on who made the vehicle, the model year, and the engine type.
P0073 Quick Info
|Meaning||Ambient Air Temperature Sensor Circuit – High Input|
|Typical Symptoms||No A/C, No Outside Temperature Display|
|Likely Causes||Bad AAT Sensor or AAT Wiring|
|Repair Difficulty||Usually Pretty Easy|
The Diagnostic trouble code (DTC) P0073 stands for “Ambient Air Temperature Sensor Circuit High Input.”
- P: Powertrain
- 0: Generic Code Type
- 0: Sub-System
- 73: Specific Malfunctioning Identifier
Here’s the definition of P0073 broken down into its two main parts:
Ambient Air Temperature (AAT) Sensor
The AAT sensor measures the air temperature outside of the vehicle’s cabin. It converts this signal to a voltage value the Powertrain Control Module (PCM) can read.
Depending on the car or truck in question, the AAT’s only function may be to display the outside air temperature. If the vehicle is equipped with a climate control system that automatically adjusts itself, it can affect the cabin air temperature.
The voltage value being returned by the AAT is too high in relation to the voltage value of the Intake Air Temp sensor and/or the Engine Coolant Temp sensor. These three should be within a few degrees of one another if the vehicle is completely cold.
Here are the most common symptoms associated with P0073:
- Malfunction Indicator/Check Engine Light has lit up
- Air Conditioning may not work
- The instrument cluster (dashboard) may not display the correct outside temperature
- The overhead compass/console may not display the correct outside temperature
There are really two main causes of P0073. Either the AAT is bad, or there is a problem with the wiring harness going to it.
- Malfunctioning ambient air emperature sensor
- Faulty Powertrain Control Module (Not very common)
- A damaged or corroded electrical connector
- Damage to the AAT sensor signal circuit
Most of the time, P0073 is going to be caused by a bad AAT sensor or AAT sensor wiring.
On most vehicles, the AAT sensor can be found around the front grill or bumper.
1. Check the AAT Wiring
You should start by looking at the Ambient Air Temperature (AAT) sensor, connection, and wires.
If the AAT wiring harness is damaged (which frequently happens due to its location), repair it and see if that clears the code.
You can read these things using a Digital Volt-Ohm Meter (DVOM) and a thermometer. Check the vehicle manual for proper readings, and if they differ significantly from your readings, replace the sensor.
You can find the correct readings inside or very close to the front bumper.
2. Check the AAT Sensor Itself
Follow through with and eliminate any other error codes before focusing on P0073. Examine the sensor itself to ensure it doesn’t look physically damaged.
In some cases, repositioning or cleaning out the terminals is the solution, but typically the culprit is a connection issue or bad sensor, whether it’s exposed or burnt wires.
Here are some brands and models notorious for having P0073 code issues:
How Serious is a P0073 Code?
This code/problem will not affect the engine, steering, brakes, fuel consumption, or the vehicle’s overall ability to go from point A to point B.
What it will cause, depending on where the vehicle is situated, is an inconvenience. The lack of air conditioning and the inability to read the outside temperature could become a major nuisance for those located in areas with hotter climates.
The number one thing P0073 affects is the auto start features climate control. If it’s hot out, the A/C will kick on. If it’s cold, the PCM will activate the heater. Most vehicles still allow you to manually control the A/C if there is an issue.
Other Related Codes
There are other codes associated with P0073. You should follow the same steps to diagnose these related issues. Check to eliminate other codes and visually inspect the sensor and the circuits that connect to the sensor for these potential issues.
- P0070 “Ambient Air Temperature Sensor Circuit Malfunction”
- P0071 “Ambient Air Temperature Sensor Range/Performance”
- P0072 “Ambient Air Temperature Sensor Circuit Low Input”
- P0074 “Ambient Air Temperature Sensor Circuit Intermittent”