P0073 is a common OBD2 trouble code that can affect the Mercury Monterey. OBD2 trouble codes. In layman’s terms, it indicates that there is an issue with your van’s ambient air sensor.
The ambient air temperature sensor (or AAT for short) is responsible for monitoring outside air temperature and regulating your vehicle’s automatic climate control system. It doesn’t affect the way your car runs or drives at all.
While P0073 is a generic code (it has the same meaning for all vehicles made after 1996), repair steps will vary depending on your Mercury Monterey’s model year and equipped options.
P0073 Quick Info
| Meaning | Ambient Air Temperature Sensor Circuit – High Input |
| Typical Symptoms | No A/C, No Outside Temperature Display |
| Likely Causes | Bad AAT Sensor or AAT Wiring |
| Breakdown Risk | No |
| Repair Difficulty | Usually Pretty Easy |
Definition
The Diagnostic trouble code (DTC) P0073 stands for “Ambient Air Temperature Sensor Circuit High Input.”
- P: Powertrain
- 0: Generic Code Type
- 0: Sub-System
- 73: Specific Malfunctioning Identifier
Here’s the definition of P0073 for the Mercury Monterey broken down into its two main parts:
1. Ambient Air Temperature (AAT) Sensor
The AAT sensor measures the air temperature outside of the van’s cabin. It converts this signal to a voltage value the Powertrain Control Module (PCM) can read.
Depending on your Monterey’s model year and options, the AAT’s only function may be to display the outside air temperature.
If your particular vehicle is equipped with a climate control system that automatically adjusts itself, it can affect the cabin air temperature (particularly when the auto start function is engaged).
2. Circuit High
The voltage value being returned by the AAT is too high in relation to the voltage value of the Intake Air Temp sensor and/or the Engine Coolant Temp sensor. These three should be within a few degrees of one another if your Monterey is completely cold.
P0073 Symptoms: Mercury Monterey
Here are the most common symptoms associated with P0073 in the Mercury Monterey:
- Malfunction Indicator/Check Engine Light has lit up
- Air Conditioning may not work
- The instrument cluster (dashboard) may not display the correct outside temperature
- The overhead compass/console may not display the correct outside temperature
P0073 Causes + Diagnosis: Mercury Monterey
There are really two main causes of P0073 in the Mercury Monterey. Either the AAT is bad, or there is a problem with the wiring harness going to it.
- Malfunctioning ambient air temperature sensor
- Faulty Powertrain Control Module (Not very common)
- A damaged or corroded electrical connector
- Damage to the AAT sensor signal circuit
Most of the time, P0073 is going to be caused by a bad AAT sensor or AAT sensor wiring.
On most vehicles, the AAT sensor can be found around the front grill or bumper. Here’s a good order to go about diagnosing P0073 in your van.
1. Check the AAT Wiring
You should start by looking at your Monterey’s Ambient Air Temperature (AAT) sensor, connection, and wires.
If the AAT wiring harness is damaged (which frequently happens due to its location), repair it and see if that clears the code.
You can read these things using a Digital Volt-Ohm Meter (DVOM) and a thermometer. Check the vehicle manual for proper readings, and if they differ significantly from your readings, replace the sensor.
You can find the correct readings inside or very close to the front bumper.
2. Check the AAT Sensor Itself
Now that you’ve checked your Monterey’s AAT wiring, it’s time to check the sensor itself.
Follow through with and eliminate any other error codes before focusing on P0073. Examine the sensor itself to ensure it doesn’t look physically damaged.
In some cases, repositioning or cleaning out the terminals is the solution, but typically the culprit is a connection issue or bad sensor, whether it’s exposed or burnt wires.
It’s likely you’ll need to replace the sensor itself, which is usually around $20 or so.
How Serious is a P0073 Code?
P0073 should not be considered a breakdown risk in the Mercury Monterey.
This code will not affect the engine, steering, brakes, fuel consumption, or your van’s overall ability to go from point A to point B.
What it will cause, is an inconvenience. The lack of air conditioning and the inability to read the outside temperature could become a major nuisance for those located in areas with hotter climates.
The number one thing P0073 affects is the auto start features climate control. If it’s hot out, the A/C will kick on. If it’s cold, the PCM will activate the heater. Most vehicles still allow you to manually control the A/C if there is an issue.
Conclusion
Replacing the AAT sensor will likely clear P0073 in the Mercury Monterey, but checking the wiring harness for damage first can save time and aggravation.