Electrical and sensors

P0072 — Ambient Air Temperature Sensor Circuit Low Input

Severity: low Safe to drive

What P0072 means

The control module feeds a reference voltage to the ambient air temperature sensor and reads the voltage drop to work out the outside temperature. P0072 sets when that signal voltage stays below the expected range. This usually points to a failed sensor or a signal wire shorted to ground, and only rarely to the module itself.

Symptoms

  • Check engine light on
  • Wrong or missing outside temperature on the dash
  • Climate control behaving oddly
  • Hard starting or rough idle in cold weather (not always)
  • Slightly higher fuel consumption

Possible causes

  1. Failed ambient air temperature sensor
  2. Signal wire shorted to ground
  3. Damaged or corroded wiring or connector
  4. Poor contact at the sensor connector
  5. Faulty input circuit in the PCM or body control module (rare)

How to diagnose

  1. Scan for codes and review freeze-frame data, then clear the code and see if it returns
  2. Check the scan tool's ambient temperature reading; an unrealistic value (such as extremely cold) points to a circuit fault
  3. Inspect the sensor (usually behind the front bumper or grille) and its connector for damage, moisture and corrosion
  4. Unplug the sensor: if the reading jumps to the opposite extreme, the signal wire is not shorted
  5. Measure sensor resistance and compare it with the spec for the current temperature
  6. Test the signal wire for a short to ground and for opens back to the module
  7. Check for the roughly 5 V reference at the sensor connector
  8. If the wiring and sensor are good, check the module's input circuit

Common fixes

  • Replace the ambient air temperature sensor
  • Repair or replace damaged wiring and connectors
  • Clean the connector contacts and secure the connector
  • Reflash or replace the control module if it is proven faulty

Questions and answers

Can I drive with a P0072 code?

Yes, usually. The fault is not a safety issue and does not disable major systems, but it is worth fixing so the outside temperature and climate control work correctly.

What most often causes P0072?

Most often it is the sensor itself or damaged wiring shorted to ground. The sensor sits at the front of the car and is exposed to water, dirt and road salt.

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.