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P0073 Code Explained: Ambient Air Temperature Sensor Circuit High Causes, Symptoms & Fixes

P0073 code displayed on an OBD-II scanner with the ambient air temperature sensor, high-voltage circuit, disconnected connector, and front bumper sensor location highlighted.

If your OBD-II scanner displays P0073, your vehicle’s Engine Control Module (ECM), Powertrain Control Module (PCM), Body Control Module (BCM), or another control module has detected higher-than-expected voltage in the ambient air temperature sensor circuit.

The generic OBD-II definition for P0073 is:

Ambient Air Temperature Sensor Circuit High

Depending on the manufacturer or scan tool, the description may appear as:

Ford’s official OBD documentation identifies P0073 as an ambient air temperature sensor circuit-high fault. Some manufacturer diagnostic procedures describe the condition as a circuit that is open or shorted to battery voltage.

The ambient air temperature sensor measures the temperature outside the vehicle. Its signal may be used by the:

P0073 is commonly caused by:

Because most ambient temperature sensors use a negative-temperature-coefficient thermistor, an open circuit or high signal voltage is often interpreted as an extremely cold outside temperature.

Possible symptoms include:

For additional diagnostic information, visit:

P0073 Quick Facts

ItemInformation
OBD-II CodeP0073
DescriptionAmbient Air Temperature Sensor Circuit High
CategoryPowertrain
SystemFuel and Air Metering
Main ComponentAmbient Air Temperature Sensor
Fault TypeHigh Circuit Voltage
Common Electrical CauseOpen Circuit or Disconnected Sensor
SeverityLow to Moderate
Safe to Drive?Usually
Typical Repair Cost$50–500

What Does P0073 Mean?

P0073 means the control module sees voltage in the ambient air temperature sensor circuit that is above the expected operating range.

The ambient air temperature sensor is usually a thermistor whose resistance changes with temperature.

In a typical negative-temperature-coefficient circuit:

When the sensor is disconnected or a wire breaks, the module may see the pull-up voltage with little or no current flowing through the sensor.

This may cause:

Ford documentation lists P0073 as a continuously monitored ambient-temperature circuit-high fault on certain diesel applications.

What Is the Ambient Air Temperature Sensor?

The ambient air temperature sensor measures the temperature of the air surrounding the vehicle.

It may be used for:

The sensor is typically mounted where it can receive outside airflow while avoiding excessive heat from the engine and radiator.

Common locations include:

Some vehicles route the ambient-temperature signal through the BCM, instrument cluster, or door module before sending the data to the PCM.

How the Ambient Air Temperature Sensor Works

Most ambient air temperature sensors are negative temperature coefficient thermistors, also called NTC thermistors.

A typical sensor uses two circuits:

  1. Signal or bias-voltage circuit
  2. Sensor-return or ground circuit

The control module supplies voltage through an internal resistor.

The sensor changes the circuit resistance according to temperature.

With a typical NTC sensor:

The module converts the measured voltage into an outside-temperature value.

The exact resistance, voltage, and calculated-temperature values vary by vehicle.

What Does “Circuit High” Mean?

“Circuit high” means the control module is receiving more voltage than expected on the sensor signal circuit.

It does not mean:

It refers specifically to the ambient temperature sensor’s electrical signal.

Common circuit-high causes include:

On many vehicles, a circuit-high condition causes the reported outside temperature to become extremely low.

Why P0073 May Display Minus 40 Degrees

An open circuit can cause the control module to see maximum signal voltage.

Because high resistance corresponds to cold temperature in many NTC circuits, the module interprets the signal as extreme cold.

The display may show:

Minus 40 is especially common because it is the same temperature on both Fahrenheit and Celsius scales.

A dashboard showing minus 40 during a summer heat wave is usually not predicting an exciting weather event. It is announcing that the sensor circuit has stopped participating.

P0070 vs P0071 vs P0072 vs P0073

CodeDescriptionTypical Meaning
P0070Ambient Air Temperature Sensor CircuitGeneral circuit malfunction
P0071Ambient Air Temperature Sensor Range/PerformanceImplausible or slow reading
P0072Ambient Air Temperature Sensor Circuit LowLow signal voltage, often short to ground
P0073Ambient Air Temperature Sensor Circuit HighHigh signal voltage, often open circuit
P0074Ambient Air Temperature Sensor Circuit IntermittentSignal changes or drops out unpredictably

In a typical NTC circuit:

Manufacturer circuit logic can differ, so always verify the vehicle’s wiring diagram and test procedure.

How the PCM Detects P0073

The monitoring module checks the ambient-temperature signal for an electrical value above its programmed limit.

P0073 may be stored when:

Some Ford applications monitor the ambient-temperature circuit continuously and can identify a high-circuit fault within a short monitoring period.

Other applications may require:

A technical bulletin for certain vehicles notes that ambient temperature may be missing or inaccurate and may require driving above 15 mph for several minutes after repair before the displayed value updates.

Symptoms of P0073

Possible symptoms include:

P0073 often has little effect on basic drivability.

The vehicle may continue to:

The most noticeable symptom may be an outside-temperature display attempting to convince the driver that northern Alaska has relocated behind the front grille.

Can P0073 Affect Air Conditioning?

Yes.

The automatic climate-control system may use ambient temperature to determine:

When the module believes outside temperature is extremely cold, it may:

This may create poor cabin cooling even when the air-conditioning system itself is mechanically healthy.

Can P0073 Affect Engine Performance?

P0073 usually does not create severe engine-performance problems.

However, ambient-temperature information may contribute to:

Possible secondary effects include:

A 2026 service bulletin lists P0073 among active or stored faults on a specific vehicle application, illustrating that the code can also appear as part of a broader module or electrical problem.

Common Causes of P0073

1. Disconnected Ambient Air Temperature Sensor

A disconnected sensor is one of the most common causes of P0073.

The connector may have been left unplugged during:

With the sensor unplugged, the module may see full pull-up voltage and interpret the circuit as open.

2. Open Ambient Temperature Sensor

The sensor may fail internally and develop an open circuit.

Possible causes include:

An open sensor will often measure infinite resistance with a multimeter.

3. Broken Signal Wire

The signal wire may break because of:

The insulation may look intact even when the conductor inside is broken.

4. Broken Sensor-Return Wire

An open return or ground circuit can also interrupt current flow through the sensor.

This may create the same electrical result as:

Test both wires rather than assuming the signal wire is always at fault.

5. Loose Electrical Connector

A connector that is not fully seated may create intermittent or permanent loss of sensor contact.

Possible causes include:

A technical bulletin involving certain trucks identifies a loose ambient-temperature sensor connector as a likely cause of P0073.

6. Corroded Connector Terminals

Corrosion can increase circuit resistance or completely interrupt the connection.

Inspect for:

A service bulletin for certain vehicles instructs technicians to inspect an A-pillar or door connector for corrosion, bent terminals, or spread terminals when P0073 is stored.

7. Water Intrusion

The sensor’s forward or mirror-mounted location makes it vulnerable to water.

Moisture may enter through:

Water may produce:

8. Front-End Collision Damage

The ambient sensor is frequently located behind the front bumper or grille.

Even a minor impact can cause:

Always ask whether the vehicle recently received front-end body work.

9. Sensor Missing After Bumper Repairs

The sensor may have been:

The dashboard may then display its coldest possible reading despite the sensor enjoying retirement somewhere in the body shop.

10. Signal Circuit Shorted to Voltage

The signal wire may contact:

Some manufacturer fault descriptions specifically associate P0073 with a circuit that is open or shorted to battery voltage.

11. Incorrect Previous Wiring Repair

Poor repairs may include:

An open or high-resistance repair can return after:

Use weather-sealed automotive repair methods.

12. Incorrectly Pinned Replacement Connector

A replacement pigtail may have:

Compare terminal positions with the wiring diagram.

Matching wire colors is helpful, but not sufficiently scientific when the previous repair also matched wire colors incorrectly.

13. Damaged Mirror-Mounted Sensor

On vehicles with a mirror-mounted ambient temperature sensor, possible causes include:

The ambient sensor may be integrated into the mirror assembly or connected through a door module.

14. Incorrect Replacement Mirror

An aftermarket mirror may:

P0073 appearing immediately after mirror replacement strongly suggests inspecting the replacement assembly and connector.

15. Incorrect Replacement Sensor

An incorrect ambient sensor may have:

A new part is not automatically the correct part.

It may simply be a cleaner way to preserve the same trouble code.

16. Harness Damage Near Active Grille Shutters

Some vehicles route the ambient-temperature wiring near active grille shutters.

Possible problems include:

Inspect the complete grille harness if the vehicle has active aerodynamic components.

17. Aftermarket Accessory Installation

Accessories installed near the front bumper may damage the sensor circuit.

Examples include:

Possible installation errors include:

18. Instrument Cluster or BCM Fault

On some vehicles, the ambient sensor connects to the:

That module then broadcasts the temperature to the PCM.

Volkswagen diagnostic information notes that P0073 may involve a high ambient-temperature error signal sent from the instrument cluster to the engine controller.

A sensor circuit may therefore be functional at one module while another module reports incorrect or missing information.

19. Network Communication Problem

A CAN communication fault may prevent valid ambient-temperature data from reaching the PCM.

Look for:

P0073 may be secondary to a network or module issue rather than a direct sensor failure.

20. PCM, BCM, or Module Software Issue

Control-module software may incorrectly interpret the ambient signal or fail to process updated data.

Possible corrections include:

Always check vehicle-specific technical service bulletins before replacing a control module.

21. Failed Control Module

A failed module input circuit can create a false high-voltage reading.

Possible affected modules include:

Module failure is uncommon.

Only suspect it after verifying:

Replacing a PCM before checking whether the sensor is still attached to the bumper is diagnosis performed with impressive confidence and very little evidence.

Is P0073 Serious?

P0073 is generally considered a low- to moderate-severity code.

The vehicle will usually continue to:

However, the code may affect:

P0073 becomes more important if:

Can You Drive With P0073?

You can usually drive with P0073 for a limited period.

The code normally does not indicate an immediate risk of internal engine damage.

You should use caution if:

The temperature display being wrong is inconvenient.

A severed harness hanging near the radiator fan deserves considerably more attention.

How to Diagnose P0073

Step 1: Scan All Available Modules

Do not scan only the engine computer.

Check the:

Look for:

Record freeze-frame data before clearing anything.

Step 2: Check the Outside-Temperature Reading

Compare:

A reading at or near the minimum programmed value often suggests:

A blank display or dashes may also indicate unavailable sensor information.

Step 3: Determine Which Module Reads the Sensor

Use a wiring diagram to determine whether the sensor connects directly to the:

This determines where voltage and continuity testing should begin.

Do not assume P0073 means the sensor is wired directly to the PCM.

Step 4: Locate the Ambient Temperature Sensor

Common locations include:

Confirm the correct sensor before disconnecting anything.

A modern front bumper may also contain:

Only one of these should be tested with an ohmmeter because the dashboard thinks it is cold.

Step 5: Inspect Recent Repair Areas

Ask whether the vehicle recently received:

If P0073 began immediately afterward, begin inspection in the disturbed area.

Step 6: Inspect the Sensor

Check for:

A missing or physically broken sensor should be replaced.

Step 7: Inspect the Connector

Look for:

A manufacturer bulletin has identified loose ambient-temperature sensor connectors as a cause of P0073 on certain applications.

Step 8: Inspect the Wiring Harness

Follow the harness toward the body or control module.

Look for:

Gently pull each wire near the connector.

A conductor broken inside its insulation may stretch even though the outer covering looks intact.

Step 9: Observe Scan Data While Disconnecting the Sensor

If the manufacturer’s procedure permits, monitor ambient-temperature data while disconnecting and reconnecting the sensor.

Possible results:

Because P0073 is already a likely open-circuit condition, this test must be interpreted carefully.

Step 10: Measure Sensor Resistance

Disconnect the sensor and measure resistance across its terminals.

Compare the result with:

Possible findings:

Step 11: Heat and Cool the Sensor

Apply controlled temperature changes using:

Monitor resistance.

A healthy NTC sensor should:

A sensor that remains open at every temperature has completed its career.

Step 12: Check Bias or Pull-Up Voltage

With the sensor disconnected and ignition on, test circuit voltage according to the wiring diagram.

The module may provide:

Do not assume every system uses exactly five volts.

Compare the reading with manufacturer specifications.

Step 13: Test the Signal Circuit for an Open

Disconnect the sensor and relevant control module as required.

Measure continuity from:

Look for:

Move the harness while watching the meter.

Step 14: Test the Return Circuit for an Open

Repeat continuity testing on the sensor-return or ground circuit.

An open return circuit can create the same symptoms as an open signal wire.

Do not stop after finding continuity on only one side of a two-wire sensor.

Step 15: Check for a Short to Voltage

With the sensor and module disconnected, inspect whether the signal circuit is receiving voltage from another source.

Possible sources include:

Some manufacturer descriptions explicitly identify P0073 as a circuit-high, short-to-battery, or open condition.

Step 16: Check Connector Terminal Tension

A terminal can appear clean yet fail to grip the sensor pin.

Use the manufacturer-approved terminal test tool.

Look for:

Terminal-tension issues may create intermittent P0073 complaints.

Step 17: Perform a Wiggle Test

Monitor scan data while gently moving:

Watch for:

Certain service bulletins direct technicians to inspect door or A-pillar connectors for terminal and corrosion problems when P0073 is present.

Step 18: Substitute a Known Resistance

When approved by the manufacturer, install a resistor representing a known ambient temperature.

Then observe scan data.

If the module displays the expected temperature:

If the reading remains at extreme cold:

Use only the specified test resistance.

Step 19: Compare Ambient Data Across Modules

Check the value reported by:

Possible findings:

Step 20: Inspect Network Communication

If ambient-temperature information is transmitted over CAN, check for:

P0073 may be stored because the PCM received an error-status message rather than because it directly measured excessive sensor voltage.

Step 21: Inspect Aftermarket Accessories

Check installations near the front bumper or mirror.

Inspect:

Look for:

Step 22: Check Technical Service Bulletins

Search manufacturer information using:

Factory bulletins have documented P0073 complaints involving loose sensor connectors, corroded door connectors, missing ambient data, wiring faults, and specific repair procedures.

Step 23: Repair the Confirmed Fault

Possible repairs include:

Use weather-sealed automotive wiring repairs.

Step 24: Verify the Repair

After completing repairs:

  1. Clear all diagnostic trouble codes.
  2. Switch the ignition off.
  3. Allow the modules to power down.
  4. Restart the vehicle.
  5. Compare ambient temperature with actual conditions.
  6. Confirm the exterior-temperature display returns.
  7. Check HVAC operation.
  8. Road-test the vehicle.
  9. Drive at moderate speed if the display requires airflow to update.
  10. Complete the required drive cycle.
  11. Confirm P0073 does not return.

Some systems update slowly after the circuit is restored. Manufacturer guidance for certain vehicles requires several minutes of driving above approximately 15 mph before the ambient-temperature display updates.

Do not declare the repair unsuccessful thirty seconds after reconnecting the sensor while the vehicle remains parked beside a hot radiator.

Common Repairs and Costs

RepairEstimated Cost
Reconnect sensor or connector$0–100
Clean electrical connector$50–150
Replace ambient temperature sensor$75–250
Repair open wiring$100–450
Replace sensor connector$75–275
Repair front bumper harness$150–600
Repair door-jamb wiring$150–700
Replace mirror-mounted sensor$150–600
Replace complete mirror assembly$300–1,500
Diagnose network communication$150–500
Update PCM, BCM, or cluster software$100–300
Replace BCM or related module$500–1,500+
Replace PCM$1,000–2,500+

Costs vary depending on:

A disconnected sensor behind an open grille may take minutes to repair.

An open wire buried inside a heated, power-folding tow mirror with cameras and enough electronics to qualify as a small apartment may be less cooperative.

Common Diagnostic Mistakes

Avoid these common P0073 diagnostic mistakes:

P0073 normally indicates a high electrical signal, not a warm day.

The dashboard may believe it is minus 40 outside because the sensor circuit is open—not because the weather has taken a sudden personal dislike to the driver.

Vehicles Commonly Affected

P0073 is a generic OBD-II code and may appear on many vehicle brands, including certain:

Application-specific P0073 issues documented in manufacturer service information include:

Always diagnose the exact vehicle rather than assuming every P0073 sensor is mounted behind the grille.

P0073 After Front Bumper Repairs

When P0073 appears after bumper, grille, radiator, or condenser work, inspect for:

The repair history is often the fastest diagnostic tool available.

A code that appeared immediately after the bumper was removed is rarely asking the technician to begin by replacing the PCM.

P0073 After Mirror Replacement

On vehicles with mirror-mounted ambient sensors, inspect:

A replacement mirror may fit the door perfectly while omitting the one inexpensive thermistor responsible for informing the entire vehicle what season it is.

P0073 in Wet Weather

P0073 that appears mainly after rain or washing may indicate:

Inspect the vehicle while the fault is active.

Electrical problems that depend on moisture frequently become model citizens after spending an afternoon drying inside a warm repair shop.

How to Prevent P0073

Reduce the likelihood of P0073 by:

Frequently Asked Questions

What does P0073 mean?

P0073 means the control module has detected voltage above the expected range in the ambient air temperature sensor circuit.

What causes P0073 most often?

Common causes include:

Is P0073 serious?

P0073 is usually low to moderate in severity.

The vehicle normally remains drivable, but climate-control, defrost, exterior-temperature display, and temperature-dependent functions may be affected.

Can I drive with P0073?

Usually, yes.

Use caution if windshield defrost, cooling fans, or other temperature-dependent systems are not operating correctly.

Does circuit high mean the outside temperature is high?

No.

“Circuit high” means the electrical signal voltage is higher than expected.

On many vehicles, this causes an extremely low displayed temperature.

Why does my car show minus 40 degrees?

A display of -40°F or -40°C commonly indicates:

The exact fallback value varies by manufacturer.

Can a disconnected sensor cause P0073?

Yes.

A disconnected ambient air temperature sensor is one of the most common causes of P0073.

Can a bad ambient temperature sensor cause P0073?

Yes.

An internally open sensor can produce excessive circuit voltage.

Can broken wiring cause P0073?

Yes.

An open signal or return wire can interrupt current flow and set P0073.

Can bumper repairs cause P0073?

Yes.

The sensor may be disconnected, omitted, damaged, or have its wiring stretched during bumper repairs.

Can mirror replacement cause P0073?

Yes, on vehicles with a mirror-mounted ambient sensor.

An incorrect mirror may omit the sensor or use incompatible wiring.

Can corrosion cause P0073?

Yes.

Corrosion may increase resistance or create an open connection.

What is the difference between P0072 and P0073?

P0072 indicates low circuit voltage, commonly associated with a short to ground.

P0073 indicates high circuit voltage, commonly associated with an open circuit or disconnected sensor.

Can P0073 affect air conditioning?

Yes.

The HVAC system may disable or limit compressor operation if it believes outside temperature is extremely cold.

Can P0073 affect the heater?

Yes.

Automatic climate-control calculations may be inaccurate when ambient-temperature data is unavailable.

Can P0073 cause limp mode?

Usually not by itself.

Reduced-power operation is possible on some applications when P0073 appears with additional electrical, software, or module faults.

Does the ambient temperature sensor require programming?

The sensor itself usually does not require programming.

The vehicle may require:

Replacement control modules may require programming.

How much does P0073 cost to fix?

A simple reconnection may cost little or nothing.

Sensor replacement often costs approximately $75–250, while wiring, mirror, network, or module repairs may cost several hundred dollars or more.

Final Thoughts

The P0073 code means the vehicle has detected high voltage in the ambient air temperature sensor circuit.

The most common causes include:

Start diagnosis by checking the exterior-temperature display.

If it shows an impossibly cold temperature:

  1. Locate the ambient sensor.
  2. Confirm it is connected.
  3. Inspect the connector and wiring.
  4. Measure sensor resistance.
  5. Test both circuit wires for continuity.
  6. Check for a short to voltage.
  7. Compare ambient-temperature data across modules.
  8. Review manufacturer technical service bulletins.

Do not confuse “circuit high” with “temperature high.” P0073 generally means signal voltage is high, and on many thermistor circuits that makes the vehicle believe it has been abandoned somewhere beyond the Arctic Circle.

Fortunately, the actual repair is often considerably warmer and simpler: reconnect a forgotten sensor, repair one broken wire, or replace a corroded two-pin connector hiding behind the bumper.

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