Electrical and sensors

P0073 — Ambient Air Temperature Sensor Circuit High

Severity: low Safe to drive

What P0073 means

The control module detected a voltage from the ambient air temperature sensor circuit that is higher than expected, or a reading that makes no sense. The sensor is a thermistor: its resistance drops as air warms up, and the module reads that as a change in voltage. A high signal usually points to an open circuit, a bad connector or a failed sensor.

Symptoms

  • Check Engine light on
  • Wrong outside temperature shown on the dash or display
  • Climate control acting erratic or incorrectly
  • Occasionally slight changes in fuel economy or idle on some vehicles
  • Temperature display showing dashes or an extreme value

Possible causes

  1. Failed ambient air temperature sensor
  2. Damaged or corroded sensor connector or terminals
  3. Open circuit in the sensor wiring
  4. Signal wire shorted to power
  5. Corroded or damaged harness near the front bumper, where water and dirt get in
  6. Rarely, a faulty ECM or climate control module input

How to diagnose

  1. Scan the vehicle and read live data for ambient temperature, then compare it with the real temperature
  2. Inspect the sensor and connector for damage, moisture and corrosion
  3. Unplug the connector and watch the reading; with an open circuit it usually goes to its minimum or maximum value
  4. Measure the sensor resistance and compare it with the spec for that temperature
  5. Check for about 5 V reference voltage and a good ground at the connector
  6. Test the wiring for opens and shorts to power, and inspect the harness along its length
  7. If the sensor and wiring are good, test the module that receives the signal

Common fixes

  • Replace the ambient air temperature sensor
  • Clean or replace the corroded connector and terminals
  • Repair the damaged section of wiring
  • Reprogram or replace the control module if the fault is confirmed

Questions and answers

What does code P0073 mean?

It means the ambient air temperature sensor circuit has a high signal. The most common causes are the sensor itself, its connector or a break in the wiring.

Can I drive with P0073?

Yes, it is usually not dangerous and barely affects the engine. The Check Engine light will stay on, though, and climate control or the temperature display may misbehave.

How do I clear P0073?

Fix the cause first by replacing the sensor or repairing the wiring, then clear the code with a scan tool. If the fault is still there, the code will return.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.