P0073 on 2019-2023 Chrysler 300: Ambient Air Temperature Sensor Fixes

What's Unique About the 2019-2023 Chrysler 300

On many modern Chrysler vehicles built on the LD platform, including the 300, the Ambient Air Temperature (AAT) sensor shares a wiring harness with the Active Grille Shutter (AGS) system. A manufacturer Technical Service Bulletin (TSB #S2008000132) directly links P0073 with code U11E9 (Lost Communication With AGS), strongly suggesting that wiring faults in this shared harness are a primary and well-documented concern for this platform, not just simple sensor failure. This makes checking the harness integrity a critical first step.

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 (Malfunction Indicator Lamp) is on.
• Incorrect outside temperature reading on the dashboard display (e.g., stuck at -40°F or '---').
• Automatic climate control system not working properly (e.g., A/C not blowing cold air).
• Active Grille Shutter (AGS) warning or related codes, particularly U11E9.
• Slightly reduced fuel economy in some cases.

Most Likely Causes

1. Damaged or Corroded Wiring/Connector 🔴 High Probability The AAT sensor and its wiring are located at the front of the vehicle, exposed to road debris, moisture, and salt. TSB S2008000132 specifically links this code to communication issues with the Active Grille Shutter, pointing to a shared harness problem. Forum users frequently report finding broken or corroded wires in the harness near the sensor or where it connects to the main fascia harness.
   How to confirm: Visually inspect the wiring harness leading to the AAT sensor and the AGS for any signs of damage, chafing, or corrosion. Pay close attention to the main front fascia harness connector. 🎬 Watch this video to understand shared active grille shutter wiring. Use a multimeter to check for an open circuit (no continuity) in the signal or ground wires. A 'wiggle test' on the harness while observing live data can help identify intermittent breaks.
   Typical fix: Repair the broken wire or replace the damaged section of the wiring harness. A common repair involves splicing in a new pigtail connector if the connector itself is corroded or damaged. Clean or replace corroded connectors and apply dielectric grease to prevent future moisture intrusion.
   Est. part cost: $15-$150
2. Failed Ambient Air Temperature (AAT) Sensor 🟡 Medium Probability → Shop Ambient Air Temperature Sensor The sensor is a simple thermistor that can fail over time due to thermal cycles and exposure to the elements, leading to an internal open circuit. However, many owners replace the sensor only to find the problem persists. A Reddit user with a Chrysler 300 reported that replacing the sensor did not fix the intermittent issue, pointing back to wiring as the more likely cause.
   How to confirm: After verifying the wiring is good, unplug the sensor and measure the resistance across its terminals with a multimeter. The reading should change when heat is applied (e.g., with a hairdryer). An open circuit (infinite resistance or 'OL') indicates a failed sensor.
   Typical fix: Replace the AAT sensor. This often requires removing the front bumper cover or splash shield for access. The sensor is typically clipped into the radiator support or bumper reinforcement bar. 🎬 Watch this step-by-step guide to replacing the sensor yourself.
   Est. part cost: $20-$75

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM): → Shop Engine Control Module (ECM) This is very uncommon and should only be considered a cause after all other possibilities, including wiring and the sensor itself, have been exhaustively tested and ruled out. A PCM failure would likely present with multiple other fault codes.

Diagnosis Steps

1. Use an OBD-II scanner to confirm the presence of P0073 and check for any other related codes, especially U11E9.
2. Observe the ambient air temperature reading on the scanner's live data or the vehicle's dashboard. A reading of -40°F or another fixed, incorrect value confirms the fault.
3. Locate the AAT sensor. It is typically mounted on the radiator support or bumper reinforcement bar, behind the front grille.
4. Visually inspect the sensor and its connector for any obvious signs of physical damage, corrosion, or loose connections.
5. Thoroughly inspect the wiring harness that connects to the AAT sensor. Trace it back as far as possible, looking for chafing, breaks, or corrosion, especially where it joins the harness for the Active Grille Shutter.
6. If the wiring appears intact, disconnect the sensor and test the harness connector. With the key on, one wire should have a 5-volt reference signal from the PCM, and the other should be a ground.
7. If voltage and ground are correct, test the sensor itself. Measure the resistance across its pins. The resistance should not be infinite (open). Use a hairdryer to gently heat the sensor; the resistance value should decrease as the temperature rises.
🎬 See how to diagnose the P0073 circuit high code.
8. If the sensor tests good and the wiring is intact, the issue may be an intermittent connection. If all else fails, the problem could, in very rare cases, be with the PCM.

Parts You'll Likely Need

• Ambient Air Temperature Sensor (OEM #5149265AB (superseded by 68518243AA)) — This is the sensor that measures the outside air temperature. It can fail internally with an open circuit, causing a 'circuit high' reading. Part number 5149265AB has been superseded by 68518243AA.
  Trusted brands: Mopar, Dorman, Crown Automotive
  OEM price range: $30-$50
  Aftermarket price range: $15-$30
• Ambient Air Temperature Sensor Connector Pigtail — Often the problem is not the sensor but the wiring or connector leading to it. A pigtail connector (e.g., Dorman 645-541) may be needed if corrosion or damage is found at the connector.
  Trusted brands: Mopar, Dorman
  OEM price range: $40-$100
  Aftermarket price range: $20-$50

Related Codes That Often Appear With This One

• U11E9 — Lost Communication With Active Grille Shutter (AGS). TSB #S2008000132 confirms that the AAT sensor and AGS share a wiring harness. A fault in this harness is a very common cause for both codes to appear together.
• P0070 — Ambient Air Temperature Sensor Circuit Malfunction. This is a more general fault code for the same circuit and may be stored alongside the more specific P0073.
• P0072 — Ambient Air Temperature Sensor Circuit Low. This indicates a short to ground, the opposite of P0073. Seeing both intermittently could suggest water intrusion in a connector causing erratic shorts and opens.

Technical Service Bulletins (TSBs) & Recalls

• S2008000132: Mentions P0073 setting alongside U11E9 due to issues with the Ambient Air Temp Sensor.
• 18-044-26: Defines P0073-00 as Ambient Air Temperature Sensor Circuit 'A' High.

Platform-Specific Known Issues

• TSB #S2008000132 explicitly links P0073 with U11E9 (Lost Communication With AGS) and an incorrectly displayed ambient air temperature, pointing to a known wiring harness issue.
• TSB #18-044-26 lists P0073-00 as 'Ambient Air Temperature Sensor Circuit 'A' High', confirming the manufacturer's definition for this fault.
• Owner experiences on forums like 300cforums.com and chargerforums.com (a platform mate) frequently cite the wiring harness behind the front bumper as the failure point, often due to chafing or corrosion from exposure to the elements.

Mechanic-Grade Diagnostic Values

• AAT Sensor Resistance — expected: Approximately 10k Ohms at 77°F (25°C), or 15.3k Ohms at 60°F (15.5°C). Resistance increases as temperature drops.. Failure: Infinite resistance (Open Loop / 'OL') or a value that does not change with temperature indicates a failed sensor.
• AAT Sensor Signal Circuit Voltage — expected: Approximately 4.6 to 5.0 Volts DC with the sensor unplugged and the key in the 'ON' position (this is the reference voltage from the PCM/TIPM).. Failure: 0 Volts indicates an open in the signal wire or a module fault. Voltage significantly over 5V could indicate a short to power.
• AAT Sensor Ground Circuit Voltage Drop — expected: Less than 100mV with the sensor plugged in and the key in the 'ON' position.. Failure: Voltage significantly higher than 100mV indicates high resistance in the ground circuit or a poor ground connection.

Scan Tool Commands That Help

• Professional Scan Tool: Sensor Simulation / Output Control — If the sensor and wiring test good, a scan tool may be able to command a simulated voltage signal to the PCM. If the PCM reading does not match the simulated input, it can help diagnose a faulty PCM input stage, though this is rare.
• Professional Scan Tool: Active Grille Shutter (AGS) System Test — If code U11E9 is present with P0073, use the scan tool to command the AGS to open and close. If it fails to respond, this confirms a fault in the AGS system or its shared wiring harness, which is the likely root cause for both codes.

Wiring & Ground Locations

• AAT Sensor Connector — Behind the front bumper cover, typically clipped to the radiator support or bumper reinforcement bar.. This is the primary point of failure due to physical damage or corrosion. One pin is the 5V reference from the control module (PCM/TIPM) and the other is the sensor ground.
• Front Fascia Harness — Runs behind the front bumper, connecting components like the AAT sensor and the Active Grille Shutter (AGS).. This harness is a known weak point. TSB S2008000132 links P0073 and U11E9, indicating a high probability of a wiring fault within this shared harness.

Real Owner Repair Stories

• Chrysler Forum user (2006 Chrysler Town & Country 3.3L (similar platform electronics)) — Check Engine Light with code P0073.
  ❌ Tried (didn't work) Replacing the sensor initially did not work because the new part from the dealer was also faulty, which caused confusion.
  ✅ What actually fixed it The final fix was repairing a broken wire in the harness leading to the sensor. The wire was naturally exposed and had broken.
• YouTube channel 'Auto Repair Questions' (2013 Chrysler 200 2.4L) — Check Engine Light with code P0073.
  ❌ Tried (didn't work) The sensor was found dangling and physically broken, likely from previous work or road damage.
  ✅ What actually fixed it Replacing the broken Ambient Air Temperature sensor and securing it properly resolved the code. The video also stresses inspecting the connector pins for damage during the repair.

When the Usual Fixes Don't Work

• While replacing the sensor is a common fix, a significant number of owners find the problem persists. A forum user on a related Chrysler platform fixed their P0073 by repairing a broken wire, but only after being confused by a brand-new replacement sensor that was also defective out of the box. This highlights that even when the diagnosis points to a simple part, the wiring should always be the primary suspect, and replacement parts themselves should not be trusted without verification.

OEM Part Supersession History

• 5149265AB, 5149025AA, 56042395 → 68518243AA — Standard part consolidation and revision by the manufacturer.
  Heads up: No known incompatibilities. The parts are physically and electrically interchangeable for the intended applications.