Fix P0073: Mechanic’s solutions that WORKED

The P0073: Ambient Air Temperature Sensor Circuit High Input code indicates a problem with the ambient air temperature sensor circuit, specifically a high input signal. This sensor is responsible for measuring the outside air temperature, which is used by various vehicle systems, including climate control. When the sensor detects a voltage reading higher than expected, it triggers this fault code.

P0073 quick overview

Meaning	P0073: Ambient Air Temperature Sensor Circuit High Input
Is it serious?	This code is typically not serious and should not cause immediate vehicle breakdown. However, it may affect certain functions like climate control.
Possible causes	– Faulty ambient air temperature sensor – Damaged or disconnected wiring to the sensor – Corrosion or poor connections in the sensor’s circuit – Environmental factors affecting the sensor’s readings
How to diagnose?	Check Sensor Location: Confirm the location of the ambient air temperature sensor, usually behind the lower grille or front bumper. Inspect Wiring and Connectors: Examine the sensor’s wiring and connectors for damage, loose connections, or corrosion. Check Sensor Condition: Inspect the condition of the ambient air temperature sensor itself to ensure it’s not damaged. Replace Sensor: If the sensor is found to be faulty, consider replacing it with a compatible replacement. Clear Diagnostic Codes: After any repairs or replacements, use a diagnostic tool to clear the fault code and monitor if it returns.

How to fix P0073 – learn from mechanics

I looked into P0073 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Cadillac

Vehicle Information:

1994 Cadillac Seville STS 4.6L

Issue + Repair History:

• Only when the engine is cold, with temperatures below 100°F, the instrument display reads “engine overheating” or “engine coolant hot” while the engine is running.
• Coolant temperature on the display reads under 100°F.
• The engine starts to run rough and then stalls, but it restarts right away.
• First-time customer.

Other OBD2 Codes + Test Results:

• P073 – Intermittent coolant temp sensor.

Suggestions to Fix Issue:

• Check the coolant temp sensor for correct temperature readings.
• Inspect the harness and wires for any issues.
• Check grounds for potential grounding problems.
• Replace the coolant temp sensor.

Final Fix:

The issue was resolved by replacing the Engine Control Module (ECM), which was identified as the cause of the problem. The ECM fixed the issue of the instrument display showing incorrect temperature readings and the engine running rough when cold.

Case #2: Jeep

Vehicle Information:

2016 Jeep Renegade Latitude 2.4L

Issue + Repair History:

• The ambient temperature sensor location was needed to resolve a problem with the outside temperature display.
• The outside temperature display would go blank and show 3 dashes when the issue occurred.
• Mitchell indicated that the sensor is in the passenger mirror, but dismantling the mirror was challenging.
• The part #68088241AA, which was a metal screw-in sensor with a 2-wire pigtail lead, was purchased but didn’t match anything on the vehicle.
• Most older models had plastic sensors located behind the grille.
• Seeking assistance from those familiar with this vehicle’s ambient temperature sensor location.

Other OBD2 Codes + Test Results:

• P0073 – Outside/Ambient air temp signal high.

Suggestions to Fix Issue:

• Investigate the underside of the front bumper, driver’s side, for the sensor’s location.
• Check inside the passenger mirror for the sensor.
• Attempt to pop off the mirror’s back cover to access the sensor.
• Move the mirror glass inboard to create a gap for releasing the mirror’s cover.
• Use a trim stick to pop off the back cover of the mirror.
• Confirm the location of the sensor by observing its response to temperature changes.
• Replace the mirror assembly if the sensor is found to be faulty.

Final Fix:

The problem was resolved by confirming the location of the ambient temperature sensor, which was inside the passenger mirror. The sensor was found to have an intermittent open in the thermistor. While the ambient air temperature sensor wasn’t available separately, the dealer replaced the entire mirror under the 3-year/36,000-mile warranty, fixing the problem.

Case #3: Chevrolet

Vehicle Information:

2016 Chevrolet Silverado 2500 HD LT 6.6L

Issue + Repair History:

• The truck had a P0073 code for the ambient temperature sensor.
• The location of the ambient temperature sensor was unclear as it didn’t match the usual locations.
• The sensor for the dashboard temperature reading is typically on the radiator support, while the one for the engine is usually in the passenger mirror.
• However, this truck did not have a sensor in the mirror.
• Seeking information from the community about alternative sensor locations.
• It was mentioned that the sensor might have been replaced with an aftermarket one.

Other OBD2 Codes + Test Results:

• P0073 – Ambient temp sensor circuit high input.

Suggestions to Fix Issue:

• Check if the ambient temperature sensor was replaced with an aftermarket one.
• Investigate whether the sensor is located behind the grille on the front bumper, similar to the 1500 trucks.
• Verify if the sensor is on the radiator support, as indicated by diagnostics.
• Consider the possibility that the sensor shares ambient air temp data with the auto AC system.
• Understand the resampling behavior of the sensor, which may require driving the vehicle for accurate readings.
• Inspect the mirror assembly for any aftermarket or incorrect parts.

Final Fix:

The issue was resolved after discovering that the customer had replaced the original mirror with an aftermarket one a few months ago. The ambient temperature sensor was indeed located in the mirror on this truck. The customer agreed to pay for an OEM mirror, and this fixed the problem.

Case #4: Mini Cooper

Vehicle Information:

2011 Mini Cooper S Clubman 1.6L

Issue + Repair History:

• The customer had overfilled the crankcase with oil, which was corrected by draining it to the right level.
• After this correction, the MIL (Malfunction Indicator Lamp) came on.

Other OBD2 Codes + Test Results:

• P186A – No information available for this code.
• P0073 – Outside temperature sensor.
• P10EB – Outside temperature sensor circuit high.

Suggestions to Fix Issue:

• Due to the lack of information for code P186A, the outside air temperature sensor was replaced.
• The sensor was found to be broken, so it was replaced as a starting point.
• The plan was to address any faults that might return after replacing the outside temperature sensor.
• No further faults were observed after replacing the sensor.

Final Fix:

The issue was resolved by replacing the outside air temperature sensor, which was broken. The sensor is typically located behind the lower grill, below the front bumper. After the replacement, no additional faults were detected. The unknown fault code P186A remains unresolved due to a lack of information, but it did not reoccur after replacing the temperature sensor.

Case #5: Dodge

Vehicle Information:

2004 Dodge Ram 3500 SLT 5.9L

Issue + Repair History:

• The technician was new to working on diesel engines.
• The map sensor had been replaced, and codes were cleared, but the vehicle still lacked power.
• A fuel line (#5) to the injector had previously ruptured, and the customer had repaired it with JB Weld and later replaced it.
• Loss of power occurred after the fuel line rupture.

Other OBD2 Codes + Test Results:

• P0514 – Battery temperature sensor.
• P0107 – MAP sensor voltage low.
• P0073 – Ambient temperature sensor.
• P2607 – Intake air heater relay 2 circuit low.
• P0108 – MAP sensor voltage too high.

Suggestions to Fix Issue:

• The technician checked for obstructions in the replaced fuel line but found none.
• Tubing from the turbo was inspected for leaks, and none were detected.
• The air filter was clean.
• The technician considered checking the lift pump for volume but was unsure at what point to check it.
• Initially, there were no codes present after replacing the MAP sensor.

Final Fix:

The issue was resolved by checking the waste gate to ensure it was not stuck or malfunctioning. A small slit was found on the hose going to the waste gate, causing a loss of boost, which resulted in a lack of turbo assistance. The technician replaced the hose, and the vehicle regained its power, with plenty of boost. No further codes were reported after this repair.

Advice	Diagnostic Step
Check the location of the ambient temperature sensor	Ensure that the ambient temperature sensor is located in the correct position, typically behind the lower grille or front bumper.
Inspect the sensor’s wiring and connectors	Examine the wiring and connectors associated with the ambient temperature sensor for any damage, loose connections, or corrosion.
Verify the condition of the sensor	Check the condition of the ambient temperature sensor itself to ensure it’s not damaged or faulty.
Replace the ambient temperature sensor	If the sensor is found to be broken or malfunctioning, replace it with a new one.
Confirm the sensor’s compatibility with the vehicle	Ensure that the replacement sensor is compatible with the specific vehicle make and model.
Clear diagnostic trouble codes (DTCs)	After performing any repairs or replacements, clear the DTCs using a diagnostic tool to reset the system and check if the fault returns.