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P0072 – Ambient Air Temperature Sensor Circuit Low Input (OBD2)

P0072 means "Ambient Air Temperature Sensor Circuit Low Input". The voltage the control unit measures in the ambient (outside) air temperature sensor circuit is below the permitted minimum. For a sensor this usually means the signal wire is shorted to ground or the reference voltage is missing; for an actuator, that its control wire is shorted to ground.

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P0072 quick summary

Fault codeP0072
MeaningAmbient Air Temperature Sensor Circuit Low Input
SystemPowertrain (Engine & Transmission)
VehiclesGeneric OBD2
SeverityLow
Can I drive?Yes. Only displays and climate comfort are affected; do not rely on the ice warning.
Repair cost€15 – €120

How the outside air temperature sensor works

The ambient air temperature sensor measures the outside temperature for the dashboard display, the climate control and some engine functions.

The sensor is usually mounted behind the front bumper or in a door mirror, where it measures outside air. It is a thermistor whose resistance falls as temperature rises. The value is used by the instrument cluster, the automatic climate control and, on some engines, for cold-start and EGR strategies.

Codes P0070–P0074 report circuit, range and intermittent faults. Because of its position, the sensor is exposed to water, salt and minor front-end impacts.

A faulty sensor typically causes a wrong outside temperature display, ice warnings at the wrong time and climate control that does not regulate properly.

On VAG vehicles (VW, Audi, Škoda, Seat, Cupra), VCDS and older VAG testers can show this code as the five-digit VAG code 16456 (P0072). Both numbers mean the same fault.

Symptoms of P0072

  • Wrong or missing outside temperature display
  • Ice warning at the wrong time
  • Climate control not regulating properly
  • Check Engine light on (some vehicles)
  • No effect on driving

Most common causes of P0072 (most likely first)

Mechanic's Pro Tip

The outside temperature display is often delayed on purpose to avoid showing heat from the engine in traffic – check the live data value before replacing the sensor.

  1. 1.Signal or control wire shorted to ground

    Most likely

    Look for chafed insulation where the harness touches the engine, exhaust brackets or body edges.

  2. 2.Missing 5 V reference or supply voltage

    An open reference wire or a shorted sensor elsewhere on the same reference circuit can pull it down.

  3. 3.Internal short in the ambient (outside) air temperature sensor

  4. 4.Failed or damaged sensor (impact, water)

  5. 5.Corroded connector behind the bumper

  6. 6.Wiring fault

  7. 7.Sensor mounted near a heat source

    Reading too high in slow traffic.

Step-by-step diagnostic guide

  1. 1

    Read codes and compare temperatures

    Read all codes. After the car has stood overnight, the ambient temperature should match the intake air and coolant temperatures.

  2. 2

    Measure the signal voltage

    With the ignition on and the ambient (outside) air temperature sensor plugged in, back-probe the signal wire. Then unplug it and check the reference/supply and ground wires separately.

    Multimeter: Signal near 0 V = short to ground or no reference. Reference wire: about 5 V with ignition on. Signal wire to ground with connector unplugged: no continuity.

  3. 3

    Inspect the sensor

    Check the sensor behind the bumper or in the mirror for damage and the connector for corrosion.

  4. 4

    Measure the sensor

    Measure resistance at a known temperature.

    Multimeter: Typical NTC: a few kΩ at 20 °C.

  5. 5

    Check wiring

    Check the wiring to the cluster or control unit.

  6. 6

    Replace and verify

    Replace the sensor and check the display after a short drive.

Frequently asked questions

Can I keep driving with P0072?

Yes. Only displays and climate comfort are affected; do not rely on the ice warning.

How much does it cost to fix P0072?

Typical repair costs are 15 € – 120 €, depending on the cause and the vehicle. The most common fixes are: signal or control wire shorted to ground; missing 5 V reference or supply voltage; internal short in the ambient (outside) air temperature sensor. Always confirm the cause with the tests above before buying parts.

Does the outside temperature sensor affect the engine?

On most cars only slightly or not at all; it mainly affects displays and climate control.

Where is the outside temperature sensor?

Usually behind the front bumper or grille, sometimes in a door mirror.

What is the difference between P0072 and similar codes?

P0072 belongs to a group of codes for the same component that differ in the type or location of the fault: P0070 – Ambient Air Temperature Sensor Circuit; P0071 – Ambient Air Temperature Sensor Range/Performance; P0073 – Ambient Air Temperature Sensor Circuit High Input; P0074 – Ambient Air Temperature Sensor Circuit Intermittent/Erratic. The tests on this page apply to the whole group; the type of fault tells you where to start.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.