Fault code P0073 – ambient air temperature sensor circuit high input

Fault code P0073 is called “Ambient Air Temperature (AAT) Sensor Circuit High Input” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P0073

The ambient air temperature sensor (AAT) converts the temperature into an electrical signal for the powertrain control module (PCM). This data is used to modify the air conditioning system operation and display the outside air temperature.

Fault code P0073 – ambient air temperature sensor circuit high input

A number of sensor signals are taken into account when performing the calculations. Outside air temperature, inside air temperature, air conditioner clutch operation, coolant temperature, and others.

If there is a problem with one of the signals, the PCM sets a corresponding diagnostic trouble code (DTC) in memory. If a high signal level is detected in the outside air temperature sensor circuit, error code P0073 is set.

To verify the fault, the PCM compares the intake air temperature (IAT) and engine coolant temperature (ECT) sensor readings. It also checks the AAT sensor voltage and compares it to the IAT / ECT readings at first cold start.

This code is set if these data differ too much. The control module also looks at the voltage signals from these sensors. To determine if they are correct when the engine is fully warmed up.

Most often the code P0073 is related to an electrical fault and is set due to problems in the circuit.

Symptoms of vehicle malfunctions

The main signal that an error P0073 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. The “Check engine” control lamp on the control panel will light up (the code will be stored in the memory as a malfunction).
  2. The air conditioner may not work properly (e.g., Auto mode failure).
  3. The outside temperature indicator may malfunction.
  4. The temperature detection by the climate control is malfunctioning.

Fault P0073 is not considered serious, as it does not affect the safety and drivability of the vehicle. The fault affects the functionality of the climate control, it may cause some inconvenience depending on the weather conditions.

Factors that can cause this error code

The error code P0073 can mean that one or more of the following problems have occurred:

  • Faulty ambient air temperature sensor.
  • Open circuit in AAT sensor signal circuit.
  • Corrosion or damage to the electrical connector.
  • Ground or voltage short circuit.
  • Road debris or other objects on the ambient air temperature sensor.
  • Sometimes the cause is a faulty PCM module.

How to fix or reset OBD-2 code P0073

Some suggested steps for troubleshooting and fix the error code P0073:

  1. Connect the OBD-II scanner to the vehicle’s diagnostic connector and read all stored data and error codes.
  2. Before continuing to diagnose code P0073, clear any other errors that may be present.
  3. Check the electrical wiring related to the ambient air temperature sensor for shorts, opens, and damage.
  4. If necessary, repair or replace any wires that are shorted, broken, damaged or corroded.
  5. Inspect the sensor connector for looseness and corrosion.
  6. Test the AAT sensor; if it is defective, replace it.
  7. If the problem persists, check and reprogram or replace the control module (PCM) if necessary.

Diagnose and repair of problems

Locate the AAT sensor, it is usually located in front of the radiator behind the grille or in the front bumper area. Once found, visually inspect the connectors and wiring.

Look for scratches, scuffs, exposed wires, burn spots, or melted plastic. Disconnect and carefully inspect the terminals inside the connectors. If necessary, clean the terminals or replace the connector.

The most common cause of error P0073 is connections. A faulty sensor comes second because of location and adverse environmental conditions.

Check the sensor and electrical circuits

If the P0073 code returns after a visual inspection and correction, the AAT sensor and its associated circuits will need to be tested. Normally there are two wires coming to the AAT sensor.

With the ignition off, disconnect the wiring harness from the AAT sensor. Turn on the ignition and use a diagnostic tool to read the AAT sensor voltage. The voltage should be about 5 volts.

Then turn off the ignition, connect a jumper to the two terminals inside the AAT harness connector, and then turn on the ignition. The reading should be about 0 volts.

If there is no 5 volts on the sensor or you see no change, the wiring from the PCM to the sensor is most likely faulty, or the PCM itself is faulty.

When all the tests are successful, but error P0073 remains, most likely the cause is a failed AAT sensor. Although a faulty control module cannot be ruled out until the AAT sensor is replaced.

On which vehicles does this problem occur most frequently

Fault code P0073 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Audi
  • BMW
  • Chevrolet (Cruze)
  • Chrysler (Sebring)
  • Dodge (Avenger, Caravan, Charger, Journey, RAM)
  • Ford (Escape, F-150, Focus, Fusion, Kuga, Mondeo, Ranger)
  • Jeep (Grand Cherokee)
  • Land Rover
  • Mazda
  • Mercedes-Benz
  • Mini (Cooper)
  • Mitsubishi (L200, Pajero)
  • Nissan
  • Volkswagen
  • Volvo
  • GAZelle (Next)

Fault code P0073 can sometimes be found with other errors. The most common are the following: P0070, P0071, P0072, P0074, U0121, U1120.


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