P0073 on 2017-2024 Chrysler Pacifica: Ambient Air Temp Sensor Causes and Fixes

What's Unique About the 2017-2024 Chrysler PACIFICA

On the Chrysler Pacifica, the P0073 code is frequently not just a simple sensor failure. It is very often linked to broader platform-specific issues, such as water intrusion into wiring connectors in the front fascia (as noted in TSB #9004290 and #0817522REVA) and problems with the Active Grille Shutter (AGS) system, which often trigger a U11E9 code simultaneously. The wiring for the AAT sensor is routed near these components, making it susceptible to damage when other parts fail or when corrosion sets in. Forum discussions on platforms like Reddit and ChryslerForum.com confirm owners frequently encounter the P0073 and U11E9 codes together, with the root cause often being a corroded wiring harness behind the radiator fan, accessible from the front wheel well.

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 is on
• Incorrect outside temperature reading on the dashboard or infotainment screen (may show a very low temperature like -40°F or -37°F).
• Automatic climate control system may not function correctly (e.g., A/C is not cold, or seat heaters turn on automatically).
• Active Grille Shutter (AGS) warning light or related codes (like U11E9) may be present.
• Cooling fans may run continuously because the computer, thinking it has lost communication with the grille shutters, defaults to a fail-safe mode.
• Start/Stop system may become unavailable.

Most Likely Causes

1. Damaged or Corroded Wiring/Connector 🔴 High Probability TSB #9004290 and TSB #0817522REVA specifically call out corrosion and water intrusion at the XY101 front fascia connector as a cause for P0073 and related codes on Pacificas. The sensor's location at the front of the vehicle exposes it to road debris and moisture. Forum users on Reddit have confirmed that a corroded wiring harness, sometimes located behind the radiator fan, was the culprit for their U11E9 and related P0073 codes.
   How to confirm: Visually inspect the AAT sensor connector and the larger XY101 harness connector for any signs of green or white corrosion, moisture, or pushed-out pins. Test for continuity and voltage at the sensor connector using a multimeter. An open circuit will result in a voltage reading above the normal range (e.g., >4.9V).
   Typical fix: Clean the connector terminals with a specialized contact cleaner. If corrosion is severe, the connector or a section of the wiring harness may need to be replaced. TSB #08-175-22 details a procedure for resealing ground G917a to prevent water intrusion on some 2022 models. Ensure the connector is properly sealed with dielectric grease after repair.
   Est. part cost: $10-$150
2. Failed Ambient Air Temperature (AAT) Sensor 🔴 High Probability → Shop Ambient Air Temperature Sensor The sensor is a simple thermistor that can fail over time due to thermal stress and exposure to the elements at the front of the vehicle. An internal open circuit in the sensor will cause the P0073 code.
   How to confirm: After confirming the wiring is good, the sensor itself can be tested. An open circuit inside the sensor will cause a P0073 code. You can test its resistance with a multimeter; it should not be an open circuit. A user on a Chrysler forum noted a good sensor had a resistance of around 12-26 ohms which changed with temperature.
   Typical fix: Replace the ambient air temperature sensor. This is a simple plug-and-play part, usually clipped into the radiator support or grille area.
   Est. part cost: $20-$75
3. Loose Sensor Connector 🟡 Medium Probability Vibrations from driving can sometimes cause the connector to become loose. TSB #9100248 specifically advises technicians to disconnect and reconnect the sensor and then drive the vehicle before ordering a new part.
   How to confirm: Physically check if the connector is securely clipped onto the sensor. Ensure the red locking tab is engaged.
   Typical fix: Disconnect the electrical connector, inspect for clean contacts, apply dielectric grease, and securely reconnect it. Clear the codes and drive the vehicle for at least 5 minutes at speeds above 15 mph to see if the code returns.
   Est. part cost: $0
4. Active Grille Shutter (AGS) System Fault 🟡 Medium Probability TSB #S2008000132 and #0817522REVA directly link P0073 with the U11E9 code for the AGS. The wiring for both systems is often bundled together, so a fault in the AGS harness can affect the AAT sensor circuit. A YouTube video shows a 2021 Pacifica with a U11E9 code where the technician suspects a faulty aftermarket AGS unit is the cause. 🎬 Watch: Why aftermarket parts might trigger communication codes.
   How to confirm: Scan for additional trouble codes. If U11E9 is present, the diagnostic process should focus on the AGS system and its shared wiring harness. You can use a capable scan tool to run a system test on the AGS to see if it opens and closes on command.
   Typical fix: Diagnose and repair the AGS fault, which may involve repairing wiring or replacing the AGS assembly. This often resolves the P0073 code 🎬 See this walkthrough for replacing the active grille shutter assembly. as well.
   Est. part cost: $100-$600

Rare But Worth Checking

• Powertrain Control Module (PCM) Fault: → Shop Engine Control Module (ECM) This is very rare. Before condemning the PCM, all other possibilities, including wiring and the sensor itself, must be exhaustively ruled out. A PCM fault usually triggers multiple other codes as well.

Diagnosis Steps

1. Scan the PCM for stored trouble codes. Note if P0073 is present alone or with other codes like U11E9.
2. Locate the Ambient Air Temperature sensor. On the Pacifica, it is typically mounted behind the front grille, often clipped into the radiator support or lower mechanical shutter.
3. Perform the step from TSB #9100248: Disconnect the sensor's electrical connector. Inspect the pins for corrosion or damage. Reconnect it securely. Clear the codes and drive the vehicle for 5 minutes at over 15 mph to see if the code returns.
4. If the code returns, inspect the wiring harness leading to the sensor. Pay close attention to the XY101 connector in the front fascia for signs of water intrusion or corrosion, as highlighted in TSB #9004290. This may require accessing the area through the front wheel well.
5. Using a multimeter, check for voltage at the sensor connector with the key on. A 'high' circuit code often means you will find an open circuit. The PCM sends a 5V reference, and if the circuit is open, you'll read close to 5V (e.g., above 4.9V).
6. If wiring appears intact and has correct voltage/ground, test the sensor itself. You can measure its resistance, which should change with temperature. An 'open' reading (infinite resistance) indicates a failed sensor.
7. If U11E9 is also present, expand your diagnosis to the Active Grille Shutter assembly and its shared wiring harness, as this is a likely point of failure.

Parts You'll Likely Need

• Ambient Air Temperature Sensor (OEM #68518243AA (replaces 5149025AA, 5149265AB)) — This is the most commonly replaced component for a P0073 code when wiring is confirmed to be intact.
  Trusted brands: Mopar, NTK, Duralast
  OEM price range: $40-$75
  Aftermarket price range: $20-$50
• Wiring Harness Connector Pigtail — If the connector at the sensor or the larger XY101 connector is corroded, replacing the connector pigtail is often necessary to ensure a solid, weather-proof connection. TSB #9004290 instructs dealers to order connector repair kits as needed.
  Trusted brands: Mopar, Dorman, Standard Motor Products
  OEM price range: $30-$60
  Aftermarket price range: $15-$40

Related Codes That Often Appear With This One

• U11E9 — Lost Communication With Active Grille Shutter (AGS). As stated in multiple TSBs (#S2008000132, #0817522REVA), the wiring for the AAT sensor and the AGS are linked. A fault in the harness often causes both codes to appear together.
• P0070 — Ambient Air Temperature Sensor Circuit Malfunction. This is a general code for the same circuit.
• P0072 — Ambient Air Temperature Sensor Circuit Low. This indicates a short to ground, the opposite of P0073, but can be caused by related wiring issues like water intrusion causing intermittent shorts and opens.

Technical Service Bulletins (TSBs) & Recalls

• 9100248: Recommends reseating the sensor connector before replacement.
• S2008000132: Links P0073 to U11E9 (AGS communication loss).
• 0817522REVA: Defines P0073 as 'Circuit High' and links it to AGS issues and water intrusion.
• 9004290: Points to corrosion at the XY101 connector in the front fascia.
• 18-044-26: Lists P0073 as a potential DTC.
• S2208000080RevA: Links P0073 to P0070-15 (AGS related).
• S2008000147 Rev.: Notes a loose AAT connector can cause P0073.
• 9004547: General diagnostic advice for a range of AAT sensor codes including P0073.

Platform-Specific Known Issues

• Water intrusion and corrosion in the XY101 front fascia connector is a known issue that can cause P0073, as documented in TSB #9004290.
• Faults in the Active Grille Shutter (AGS) system are common and frequently trigger P0073 alongside U11E9 due to shared wiring harnesses, as noted in TSBs #S2008000132 and #0817522REVA.

Mechanic-Grade Diagnostic Values

• AAT Sensor Connector Voltage — expected: ~5.0V on the reference wire with key on, engine off, sensor disconnected.. Failure: With the sensor disconnected, measuring the signal wire will show a voltage above 4.9V, confirming the 'Circuit High' condition seen by the PCM. A Chrysler-specific diagnostic step checks for voltage above 5.2V.
• AAT Sensor Resistance — expected: A specific Ohm-to-temperature chart for the Mopar sensor is not publicly available. However, a functional sensor will show a clear resistance reading (not an open circuit/infinite resistance) that changes when temperature is applied (e.g., with a heat gun).. Failure: A reading of infinite resistance (Open Line) indicates a failed sensor.

Scan Tool Commands That Help

• wiTECH or equivalent professional scanner: Active Grille Shutter (AGS) Actuator Test — When P0073 is accompanied by U11E9, this bidirectional command forces the AGS to open and close, verifying if the actuator motor is functional and if the PCM can control it.
• wiTECH or equivalent professional scanner: Reset AGS Counter — This function is required after installing a new Active Grille Shutter assembly. Chrysler vehicles track the number of shutter open/close cycles, and this counter must be reset to zero for the new component.

Wiring & Ground Locations

• XY101A — The main dash-to-front-fascia harness connector, located in the driver's side front wheel well area.. This connector is cited in TSB #9004290 as a common location for water intrusion and corrosion, which can cause an open or short in the AAT sensor circuit, triggering P0073 and often U11E9.
• G917a — A ground point in the front engine bay area.. TSB #08-175-22 for 2022 models specifically involves resealing this ground with tape and zip ties to prevent water intrusion that leads to codes P0073 and U11E9, indicating it's a known weak point.
• AGS Connector — At the bottom of the Active Grille Shutter assembly, behind the front bumper cover.. This connector and its associated wiring are extremely vulnerable to road debris, snow, and impact damage, often leading to broken wires or corrosion that causes U11E9 and P0073.

Real Owner Repair Stories

• South Main Auto LLC YouTube Channel (2018 Chrysler Pacifica) — Check Engine Light with code U11E9 (Lost Communication with AGS). P0073 is commonly associated.
  ❌ Tried (didn't work) Replacing the Active Grille Shutter (AGS) assembly., Replacing the front wiring harness with a new one from Chrysler.
  ✅ What actually fixed it The technician found a service bulletin noting a wiring pinout change for the AGS connector on vehicles built on or after April 11, 2018. The vehicle was built in January 2018, but the new replacement harness was wired for the newer configuration. The communication wire was in the wrong pin location on the new harness. The technician had to de-pin the connector on the brand new harness and move the wires to match the pre-April 2018 layout to restore communication and clear the code.
• RamForum.com user (Ram 1500 (shares AGS system with Pacifica)) — Check Engine Light with code U11E9.
  ❌ Tried (didn't work) Resetting the PCM., Verifying the AGS motor was functional (it would self-test on startup)., Visually inspecting the harness for obvious damage.
  ✅ What actually fixed it The owner found the issue after extensive diagnosis. The LIN bus wire for the AGS had corroded and broken *inside* the protective plastic wire loom, so it was not visible externally. He discovered it when testing for voltage and noticed the reading was intermittent. Pulling back the loom revealed the corroded, broken wire. Repairing this single wire fixed the U11E9 code.

OEM Part Supersession History

• 5149025AA, 5149265AB, 56042395 → 68518243AA — Standard part consolidation and revision over time.

Model Year Variations Within This Range

• 2017 - 2018 (built on or before April 10, 2018): The wiring pinout for the Active Grille Shutter (AGS) connector is different from vehicles built after this date. When replacing the AGS assembly or harness on an early model with a newer part, the connector must be manually re-pinned to the old configuration to establish communication and prevent a U11E9 code.
• 2022 (built on or before April 25, 2022): These vehicles are subject to TSB 08-175-22, which involves resealing ground point G917a and connector XY101A to prevent water intrusion that causes P0073 and U11E9. This implies later models may have an improved seal from the factory.