P0073 on 2016-2019 Ford Explorer: Ambient Air Temperature Sensor Causes and Fixes

What's Unique About the 2016-2019 Ford EXPLORER

The 2016-2019 Ford Explorer has a well-documented, specific issue that triggers the P0073 code, but it primarily affects the Police Interceptor Utility sub-model. Ford issued two Technical Service Bulletins (TSBs) highlighting that non-Ford upfitters often disconnect a specific wiring harness (C134) when removing the front bumper to install push bars or other police equipment, and then fail to reconnect it. This single issue is the most common cause for this code on police models and should be the first thing checked.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light (MIL) is illuminated
• Inaccurate outside temperature display on the dashboard (often showing a default low value like -40°F or "--").
• Automatic climate control system does not work correctly or defaults to a specific mode.
• Air conditioning (A/C) will not blow cold air because the system believes the outside temperature is too low to safely engage the compressor.

Most Likely Causes

1. Disconnected C134 Wiring Connector (Police Interceptor Models) 🔴 High Probability As documented in Ford TSBs SSM 47529 and SSM 46338, third-party upfitters installing police accessories frequently disconnect this harness to remove the front bumper and forget to reconnect it. This is the number one cause for this code on PIU models.
   How to confirm: Visually inspect wiring connector C134. 🎬 Watch: Locate the C134 connector on Police Interceptor models. It is a large, multi-pin connector located behind the front bumper, often near the driver's side frame rail. Check to see if it is disconnected. This should be the very first check on any Police Interceptor Utility model.
   Typical fix: Reconnect the C134 wiring connector.
   Est. part cost: $0
2. Failed Ambient Air Temperature (AAT) Sensor 🔴 High Probability → Shop Ambient Air Temperature Sensor The sensor is located in the front of the vehicle, typically behind the grille, making it susceptible to damage from road debris, moisture, and front-end impacts. Internal failure of the thermistor will create an open circuit, triggering the P0073 code.
   How to confirm: After checking wiring, test the sensor. Disconnect it and use a multimeter to check for resistance across its two pins. An open circuit (infinite resistance or 'OL') indicates a failed sensor. A healthy sensor's resistance will change when warmed or cooled.
   Typical fix: Replace the AAT sensor. It is typically held in by a simple plastic clip and can be accessed through the grille.
   Est. part cost: $20-$45
3. Damaged Wiring or Connector 🟡 Medium Probability The wiring to the AAT sensor is in an exposed location and can be damaged by road debris, corrosion from road salt, or improper service procedures. The connector itself can also corrode or have pins back out.
   How to confirm: Visually inspect the wiring harness leading to the sensor for any breaks, corrosion, or loose pins in the connector. Use a multimeter to check for the 5-volt reference signal at the connector with the key on. Wiggling the harness while watching a live data scan tool can reveal intermittent breaks.
   Typical fix: Repair the damaged section of the wire or replace the connector pigtail. In a documented case, a user fixed the issue by replacing the connector itself, not the sensor.
   Est. part cost: $10-$30

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) This is extremely rare and should only be considered after the sensor and all wiring have been exhaustively tested and confirmed to be good. Other DTCs would likely be present if the PCM were failing.

Diagnosis Steps

1. Read the trouble codes with an OBD-II scanner.
2. If the vehicle is a Police Interceptor Utility, immediately locate and inspect wiring connector C134 behind the front bumper cover to ensure it is fully seated. This is the most likely cause per TSBs SSM 47529 and SSM 46338.
3. For all models, check the live data from the AAT sensor on the scanner. A reading of -40°F/-40°C or another extreme default value strongly suggests an open circuit, consistent with P0073.
4. Locate the AAT sensor. It is mounted behind the front grille, near the center of the radiator support, often visible and accessible through the grille openings.
🎬 Watch this quick 5-minute fix for the ambient temp sensor.
5. Visually inspect the sensor and its electrical connector for any signs of physical damage, corrosion, or loose wires.
6. Disconnect the sensor. Use a multimeter to test for a reference voltage (typically around 5 volts) at the harness connector with the key on. No voltage indicates a wiring problem upstream.
7. Test the sensor itself. Measure the resistance across the two pins of the sensor. It should not be an open circuit (infinite resistance). A typical Ford sensor might read around 37k Ohms at 32°F (0°C) and 9.5k Ohms at 77°F (25°C). An open reading means the sensor is bad.
8. If the sensor tests good and the connector has voltage, thoroughly inspect the entire length of the wiring harness for breaks, chafing, or damage. A user on Reddit noted their connector plug was smashed and wrapped in tape, causing the issue.
9. If the sensor and wiring are confirmed to be good, the issue may be with the PCM, but this is highly unlikely.

Parts You'll Likely Need

• Ambient Air Temperature Sensor (OEM #DY-1390) — This sensor is the most common part to fail on non-police models, causing the P0073 code. Motorcraft is the OEM brand.
  Trusted brands: Motorcraft, Standard Motor Products
  OEM price range: $30-$50
  Aftermarket price range: $15-$30

Related Codes That Often Appear With This One

• P0071 — This code indicates a range/performance issue with the AAT sensor, which can be triggered by intermittent connection problems that also cause P0073.
• P0072 — This indicates a 'Circuit Low' condition (a short to ground), which is the opposite of P0073. Seeing both could point to erratic wiring shorts or an intermittent sensor failure.
• P0074 — This indicates an intermittent circuit fault and is often seen with P0073, especially in cases of loose connections or damaged wiring. Ford TSBs for other models have listed P0073 and P0074 together for similar issues.

Technical Service Bulletins (TSBs) & Recalls

• SSM 47529: "Some 2016-2019 Police Interceptor Utility vehicles may have an illuminated MIL with ambient air temperature (AAT) sensor DTC P0073. During the installation of certain police accessories by non-Ford vehicle upfitters, wiring connector C134 may have been left disconnected..."
• SSM 46338: "SOME 2016-2017 EXPLORER POLICE UTILITY VEHICLES MAY HAVE AN ILLUMINATED MIL WITH AMBIENT AIR TEMPERATURE SENSOR DTC P0073. DURING THE INSTALLATION OF CERTAIN POLICE ACCESSORIES BY NON-FORD VEHICLE UPFITTERS, WIRING CONNECTOR C134 MAY HAVE BEEN LEFT DISCONNECTED..."

Platform-Specific Known Issues

• Police Interceptor Utility Models: TSBs SSM 47529 and SSM 46338 state that during the installation of police accessories by non-Ford upfitters, wiring connector C134 may be left disconnected after reinstalling the front bumper cover, directly causing a P0073 code. The bulletins advise checking this connector first before performing any other diagnostics. This is a widely confirmed issue in owner forums.

Mechanic-Grade Diagnostic Values

• AAT Sensor Resistance vs. Temperature — expected: Approx. 32.7k Ω at 32°F (0°C), 12.5k Ω at 68°F (20°C), 9.8k Ω at 78°F (25.6°C). Resistance is inversely proportional to temperature.. Failure: Infinite resistance (Open Loop / 'OL') at any temperature indicates a failed sensor.
• AAT Signal Circuit Voltage (at PCM) — expected: Varies based on temperature, typically under 4.5V.. Failure: A reading that is topped out at the reference voltage (approx. 4.6V - 5V) indicates an open circuit, which is the cause of P0073.
• Sensor Ground Circuit Resistance — expected: Below 5.0 Ohms.. Failure: Resistance above 5.0 Ohms indicates an open or high resistance in the ground circuit between the sensor connector and the PCM.

Hidden / Shadow Codes Worth Checking

• B1255: On some Ford platforms (e.g., 2006 Explorer), the Instrument Panel Cluster (IPC) can set this Body code for an open Ambient Air Temperature Sensor circuit, even if the PCM sets P0073. This indicates that modules other than the PCM also monitor this sensor. (see via A scan tool capable of reading Body Control Module (BCM) or Instrument Panel Cluster (IPC) codes.)

Scan Tool Commands That Help

• Ford IDS (Integrated Diagnostic System) or equivalent: AAT Sensor Data Reset — After replacing the AAT sensor, the filtered sensor data in the PCM must be reset. According to a Ford General Service Bulletin, this can be done with a specific reset procedure in the scan tool or by driving the vehicle at speeds consistently above 20 MPH for at least 5 minutes. Failure to do so may result in the temperature display remaining incorrect and the A/C staying inoperative even with a new sensor.

Wiring & Ground Locations

• AAT Sensor PCM Pins (C2280B) — At the Powertrain Control Module (PCM) connector C2280B.. For testing continuity: the AAT signal wire is Yellow/Green and connects to Pin 47. The Signal Return (sensor ground) wire is White/Violet and connects to Pin 30. Testing for voltage at the connector and continuity back to these pins can isolate a wiring fault from a sensor or PCM fault.
• C134 — Large multi-pin connector located behind the front bumper, often near the driver's side frame rail. Connects the main body harness to the front bumper/grille harness.. This is the specific connector cited in TSBs SSM 47529 and SSM 46338 as being frequently left disconnected on Police Interceptor models after upfitter work, directly causing the P0073 open circuit.
• G103 / G104 — G103 is at the left front corner of the engine compartment; G104 is on the right side of the engine compartment.. These are the main chassis ground points for the front of the vehicle. While the AAT sensor uses a dedicated signal return to the PCM, a poor main ground connection in this area can cause a variety of strange electrical issues, and they are worth inspecting for corrosion or looseness if circuit testing yields confusing results.

Real Owner Repair Stories

• Ford Truck Enthusiasts Forum user 'Mark H' (2017 Ford Explorer (Ecoboost 4-cylinder)) — Check Engine Light with a code for the AAT sensor after replacing the A/C condenser.
  ✅ What actually fixed it The user realized they had forgotten to reconnect the main wiring harness connector that links the engine bay to the front grille/bumper harness during reassembly. Reconnecting it solved the problem.
• YouTube channel 'Nick's Garage' (2016 Ford Explorer (2.3L)) — No A/C and P0073 code.
  ❌ Tried (didn't work) Replacing the Ambient Air Temperature sensor.
  ✅ What actually fixed it The problem persisted after replacing the sensor. Using an oscilloscope, the mechanic found that wiggling the sensor's electrical connector caused the signal to drop out. The connector pigtail itself was faulty, creating the open circuit. Replacing the pigtail fixed the issue.
• YouTube channel 'Autel Tech' (2014 Ford F-250 (different model, but same principle)) — P0073 code, climate control issues.
  ❌ Tried (didn't work) Initial visual inspection.
  ✅ What actually fixed it The vehicle had an aftermarket passenger mirror installed (where the AAT sensor is located on this truck). The aftermarket mirror assembly did not come with the sensor pre-installed. The fix was to locate the unplugged pigtail tucked inside the mirror housing and install a new sensor into it.

OEM Part Supersession History

• DY-1345, FC4Z-12A647-A → AU5Z-12A647-B — Part has been updated or consolidated by the manufacturer.
  Heads up: The Motorcraft service part number is typically DY-1390 for the 2016-2019 Explorer application.

Model Year Variations Within This Range

• 2016-2019: While the 2016-2019 Explorer typically has the AAT sensor behind the grille, technicians should be aware that on other Ford platforms of the same era, the sensor may be located in the passenger-side exterior mirror. Always physically verify the location before ordering parts.