P0073: Ambient Air Temperature Sensor High Input

What does P0073 actually mean?

The computer reads the voltage from the ambient air temperature sensor and finds it consistent with an implausibly high resistance, most often meaning an open circuit rather than genuinely hot outside air.

The code sits in the ambient air temperature sensor area and is reported by the comprehensive component monitor. It names the circuit or the condition where the computer saw a reading outside its expected range. It does not name a failed part, and several genuinely different faults set this same code, which is the whole reason the causes below are ordered rather than listed.

What people usually notice

• Outside temperature display reads implausibly hot or blank
• Check engine light
• No change in engine performance

Why does P0073 set?

The causes below are ordered by how often they turn out to be the answer, cheapest and most common first. That order matters more than the list itself: the expensive component named in the code text is very rarely the first thing to replace, and working down from the top is what stops a ambient air temperature sensor fault becoming an expensive guess.

Corroded or disconnected connector at the sensor is the one to rule out before anything else. The most common and cheapest cause given the exposed front bumper mounting location.

The order worth checking on P0073

Start with freeze frame. Vehicle speed at the fault helps rule out a heat soak reading taken while parked right after driving. That snapshot is taken at the instant the code set, and it is the single most useful piece of evidence you have, which is also why clearing the code before reading it is such a costly habit.

This code is diagnosed by watching values change rather than by reading the number again, so the tool has to stream live data and hold freeze frame. Reading the live sensor voltage confirms whether it is pinned at the value expected from an open circuit.

The order worth working in

• 1. Corroded or disconnected connector at the sensor: The most common and cheapest cause given the exposed front bumper mounting location.
• 2. Broken wire between the sensor and the computer: Front end collision repair or car washes can loosen or damage this wiring.
• 3. Failed ambient air temperature sensor: The internal element can open completely with age.
• 4. Water intrusion causing an intermittent open: Can create a fault that comes and goes with weather.

Is it safe to drive with P0073?

This does not affect how the vehicle drives and is safe to schedule as a routine repair.

This is a severity 1 of 4 code. It will not usually strand you, but it will fail an emissions test while it is present, and the underlying fault rarely gets cheaper by being left alone.

What does it cost to ignore P0073?

The practical cost is limited to an inaccurate temperature display and a lit check engine light, since this sensor plays a minor role in core engine control on most vehicles.

There is also the diagnostic cost of waiting. Freeze frame data, pending code history and the readiness monitor state all describe the fault as it was when it set, and all of it is lost the moment somebody clears the code to make the lamp go out.