P0073 on 2016-2023 Ram 1500: Ambient Air Temperature Sensor Causes and Fixes

What's Unique About the 2016-2023 Ram 1500

The 2016-2023 Ram 1500 range spans two distinct generations: the 4th Gen 'Classic' (DS) and the 5th Gen (DT, 2019+). The location of the AAT sensor is a key difference. On most 4th and 5th Gen Rams, the sensor is located in the driver's side mirror. This placement makes the wiring that runs through the door jamb a common failure point due to repeated opening and closing of the door. Furthermore, the black plastic mirror housing gets 'heat soaked' in direct sunlight, causing inaccurate high temperature readings even with a functional sensor. Aftermarket tow mirrors are also a frequent cause of this code if they are not equipped with the correct sensor or harness.

Diagnostic Flowchart

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

Generation note: The 2016-2023 period covers the end of the 4th Generation Ram 1500 (DS), sold as the 'Classic' from 2019 onwards, and the 5th Generation (DT), which launched in 2019. While both generations can experience this code, the primary cause—a faulty sensor or wiring—is similar. The sensor's location in the driver's side mirror is a known weak point for both. Some earlier 4th Gen models or different trims may have had the sensor behind the grille or on the radiator support, a location confirmed by some Ram 2500 owners. Always verify the location on your specific truck before starting repairs.

Symptoms You May Notice

• Check Engine Light is on.
• Incorrect outside temperature display, often showing a default low value like -40°F.
• Automatic climate control (A/C and heat) does not work properly or at all.
• Remote start features tied to temperature (like heated seats/wheel) may not activate correctly.

Most Likely Causes

1. Faulty Ambient Air Temperature (AAT) Sensor 🔴 High Probability → Shop Ambient Air Temperature Sensor The sensor is exposed to the elements, making it susceptible to moisture, corrosion, and physical damage. In one documented case, the tip of the sensor had dry-rotted and broken off completely. Aftermarket mirror assemblies may also contain low-quality sensors that fail prematurely.
   How to confirm: Unplug the sensor and test its resistance with a multimeter. Compare the reading to a temperature/resistance chart in the service manual. An infinite resistance (open circuit) reading indicates a failed sensor.
   Typical fix: Replace the ambient air temperature sensor. This is often a small, inexpensive part that can be accessed by removing a small panel on the bottom of the driver's mirror.
   Est. part cost: $15-$40
2. Damaged Wiring or Connector 🔴 High Probability For trucks with the sensor in the driver's mirror, the wiring harness that passes through the door jamb boot is constantly flexing. This is a well-known failure point on Ram trucks, leading to broken wires over time. The connector itself can also suffer from corrosion or pushed-out pins.
   How to confirm: Visually inspect the wiring going to the sensor, especially where it passes from the door into the truck's body. Check the connector for corrosion or pushed-out pins. Use a multimeter to check for a 5V reference signal and ground at the connector with the key on.
   Typical fix: Repair the broken wire(s) by soldering in a new section and using heat-shrink tubing, or replace the damaged connector pigtail.
   Est. part cost: $10-$30
3. Incorrect Aftermarket Tow Mirrors 🟡 Medium Probability Many Ram 1500 owners install aftermarket tow mirrors. If these mirrors do not include a compatible AAT sensor, or if the wiring harness is incorrect, it will immediately trigger a P0073 code. 🎬 Watch: Fix P0073 after installing tow mirrors on 2013-2018 Rams
   How to confirm: If the code appeared immediately after installing new mirrors, this is the most likely cause. The mirrors are missing the sensor circuit.
   Typical fix: Install a dedicated temperature sensor harness, which is available from aftermarket suppliers like Boost Auto Parts (part #2843), to add the sensor circuit to the mirror. 🎬 See how to add an AAT sensor to 2019-2024 tow mirrors
   Est. part cost: $30-$50

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM) or Body Control Module (BCM): → Shop Engine Control Module (ECM) This is very rare. In one forum instance, after replacing sensors and wiring to no avail, a BCM replacement ultimately fixed the issue. Before condemning a control module, all other possibilities must be exhaustively ruled out.
• Blown Fuse: In some cases, a fuse related to the sensor's circuit could be blown. On 2013-2018 Rams, fuse F99 in the main engine fuse box has been associated with temperature sensor circuits. Always check fuses before replacing more expensive components.
• Faulty Driver Door Module (DDM): Extremely rare, but documented on owner forums. Since the AAT sensor data is routed through the DDM, a fault within the module itself can cause a P0073 code even with a good sensor and wiring. One owner reported this was the final fix after multiple sensor replacements failed. This often appears with other door-related codes like U113D-00.

Diagnosis Steps

1. Verify the P0073 code is present using an OBD-II scanner.
2. Check the outside temperature reading on the dashboard. An illogical value (like -40°F) strongly suggests an AAT circuit fault.
3. Identify your Ram's generation and visually confirm the sensor's location. It is most likely in the bottom of the driver's side mirror, but some trims may have it behind the grille.
4. Carefully inspect the sensor and its connector for any visible damage, corrosion, or loose wires.
5. Thoroughly inspect the wiring harness inside the rubber boot between the driver's door and the truck's A-pillar for any signs of chafing or broken wires.
6. With the ignition on, disconnect the sensor and use a multimeter to test for a 5-volt reference signal at the connector.
7. If voltage and ground are good, test the sensor itself. Measure the resistance across the sensor's pins and compare it to the manufacturer's specifications. If the resistance is infinite (Open Line), the sensor is bad.
8. If the code appeared after installing aftermarket mirrors, confirm they have the correct AAT sensor. If not, purchase and install a compatible sensor harness.
9. As a final check, the PCM performs a rationality test after an 8-hour cold soak by comparing AAT, Intake Air Temp, and Coolant Temp readings at key-on. A major discrepancy can point to the AAT circuit.

Parts You'll Likely Need

• Ambient Air Temperature Sensor (OEM #5149264AB (replaces 5149264AA, 5293138AA)) — This is the most common point of failure for this code, either due to internal failure or physical damage from exposure.
  Trusted brands: Mopar, Dorman, Standard Motor Products
  OEM price range: $25-$50
  Aftermarket price range: $15-$30
• Ambient Air Temperature Sensor Harness (for aftermarket mirrors) — Required when installing aftermarket tow mirrors that do not come with a built-in AAT sensor, which is a very common cause of P0073 on these trucks.
  Trusted brands: Boost Auto Parts
  OEM price range: N/A
  Aftermarket price range: $30-$50

Related Codes That Often Appear With This One

• P0070 — General fault code for the Ambient Air Temperature Sensor Circuit.
• P0072 — Indicates Ambient Air Temperature Sensor Circuit Low, the opposite of P0073, suggesting a short to ground instead of an open circuit. Both are cited in TSB #18-044-26.
• U113D-00 — A communication code, 'Lost Communication with Master Power Window Switch'. Since the AAT sensor is in the driver's mirror and its data is routed through the Driver Door Module (DDM), a wiring issue in the door can cause both codes to appear together, as noted in TSB #S2208000162.

Technical Service Bulletins (TSBs) & Recalls

• Bulletin #18-044-26: Mentions P0073-00 - Ambient Air Temperature Sensor Circuit "A" High as a potential stored code during engine diagnostics.
• Bulletin #S2208000080: Links P0073 to a missing ambient air temperature signal, describing it as 'Ambient Air Temperature Sensor Circuit High'.
• Bulletin #S2208000162: Critically links DTC P0073 with U113D-00 ('Lost Communication with Master Power Window Switch'), pointing towards a wiring or module issue within the driver's door, where the AAT sensor is located.

Platform-Specific Known Issues

• Mirror Sensor Location and Heat Soak: On 5th Gen (2019+) and later 4th Gen Ram 1500s, the AAT sensor is located in the driver's side mirror. This makes the wiring in the door jamb a frequent failure point and can also lead to inaccurate readings. As one owner on a forum noted, 'The whole mirror housing gets heat soaked when the sun is beating directly on it. This awful location is why our temps read so high and inaccurately.'
• Aftermarket Tow Mirrors: A significant number of P0073 codes on Ram trucks are self-inflicted by owners installing aftermarket tow mirrors that lack the AAT sensor. This requires a separate harness, like the one from Boost Auto Parts, to be wired into the driver's side mirror connector to resolve the Check Engine Light.
• Door Jamb Wiring Failure: The wires inside the flexible rubber boot between the driver's door and the cab are known to fatigue and break from repeated opening and closing. This is a primary cause of P0073 when the sensor itself tests as good.

Mechanic-Grade Diagnostic Values

• AAT Sensor Resistance — expected: Approximately 9.45 kOhms at 79°F (26°C) and 2.488 kOhms at 130°F (55°C). The resistance should be around 336 kOhms at -40°F (-40°C).. Failure: Infinite resistance (Open Line) or a reading that doesn't change with temperature indicates a faulty sensor.
• AAT Sensor Connector Voltage (Key On, Sensor Disconnected) — expected: Approximately 5.0 to 5.57 volts on the signal wire.. Failure: Voltage above 5.2V could indicate a short to voltage. No voltage could indicate a broken wire or module issue.
• AAT Signal Circuit Resistance (AAT connector to DDM connector) — expected: Below 5.0 Ohms.. Failure: Resistance above 5.0 Ohms indicates an open or high resistance in the (G31) AAT Signal circuit.

Scan Tool Commands That Help

• wiTECH or equivalent professional scan tool: Read Active DTCs in DDM and BCM — Before diagnosing P0073 in the PCM, check for any communication DTCs (like U-codes) or AAT-related faults in the Driver Door Module (DDM) and Body Control Module (BCM), as the sensor data passes through them first. Resolving these is critical before proceeding.
• wiTECH or equivalent professional scan tool: View Live Data for AAT — To observe the temperature value being reported by the sensor to the modules in real-time. This can help determine if the reading is stuck, erratic, or rational compared to other temperature sensors on the vehicle.

Wiring & Ground Locations

• (G31) AAT Signal Circuit — This is the specific circuit wire that carries the temperature signal from the AAT sensor to the Driver Door Module (DDM).. A break (open) or high resistance in this wire is a direct cause of P0073. Diagnostic procedures specifically call for testing the continuity and resistance of this circuit between the sensor and the DDM.
• Driver Door Module (DDM) — Located inside the driver's door panel.. The AAT sensor wires connect directly to the DDM. The DDM processes the sensor's resistance reading and sends the temperature data over the CAN bus to the BCM, which then forwards it to the PCM. A fault in the DDM can cause P0073 even if the sensor and wiring are good.
• Door Harness Connector — The large connector located in the jamb area between the driver's door and the A-pillar, inside a flexible rubber boot.. This is the most common location for wire fatigue and breakage due to the repeated motion of the door opening and closing. The (G31) AAT signal wire passes through this connector and is a frequent point of failure.

Real Owner Repair Stories

• Reddit user Loud_Maize7683 (2022 Ram 1500 Laramie) — Check Engine Light on with code P0073, and A/C not working properly.
  ❌ Tried (didn't work) Replacing the Ambient Air Temperature sensor three separate times.
  ✅ What actually fixed it The issue was ultimately a faulty Driver Door Module (DDM).

OEM Part Supersession History

• 5293138AA, 5149264AA → 5149264AB — Standard part revision and consolidation over time.

Model Year Variations Within This Range

• 2019-2023 (DT) vs 2016-2018 (DS): While the AAT sensor location in the mirror is common, the internal electronics and module architecture differ between the 4th Gen (DS) and 5th Gen (DT) platforms. The data path (AAT > DDM > BCM > PCM) is conceptually similar, but the specific modules, connectors, and software can vary, making it crucial to use the correct wiring diagram for the specific year and generation.