P0070 on 2016-2023 Ram 1500: Ambient Air Temperature Sensor Circuit Fault Guide

What's Unique About the 2016-2023 Ram 1500

For many 4th and 5th generation Ram 1500s, the ambient air temperature sensor is located in the driver's side mirror housing. This placement makes it vulnerable to damage from side impacts and can cause inaccurate readings due to the black plastic housing getting 'heat soaked' in direct sunlight. Furthermore, the wiring that runs through the flexible boot between the door and the truck body is a known weak point, often leading to broken wires from repeated opening and closing of the door. TSB S2208000080 specifically calls out inspecting the G31 and G931 circuits from the sensor in the mirror, to the Driver Door Module (DDM), and then to the Body Control Module (BCM), confirming this common failure path.

Diagnostic Flowchart

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

Generation note: This range covers the end of the 4th generation (2016-2018 and 'Classic' models) and the 5th generation (2019-2023). On both generations, the AAT sensor is commonly found in the driver's side mirror. However, some earlier 4th gen models or different trims may have the sensor located behind the front grille. It is important to visually confirm the location on your specific truck before ordering parts.

Symptoms You May Notice

• Check Engine Light is on.
• Inaccurate or blank outside temperature display on the dashboard or infotainment screen (often defaults to -40°F or -40°C).
• Automatic climate control system not working properly or blowing air at the wrong temperature.
• Air conditioning may not engage, especially if the system thinks the outside temperature is freezing.

Most Likely Causes

1. Failed Ambient Air Temperature Sensor 🔴 High Probability The sensor is a simple thermistor that can fail over time. Its location in the mirror on many Rams makes it susceptible to weather and physical damage.
   How to confirm: After locating the sensor, test its resistance with a multimeter. The resistance should change predictably with temperature. An infinite resistance (open) or zero resistance (short) indicates a failed sensor. 🎬 Watch: A guide to testing sensor resistance with a multimeter. A forum post for a similar Dodge vehicle noted resistance values of 336 kOhms at -40°F and 2.488 kOhms at 131°F. A common value at room temperature is around 10 kOhms.
   Typical fix: Replace the ambient air temperature sensor. This often involves removing a small panel on the bottom of the driver's side mirror.
   Est. part cost: $15-$50
2. Damaged Wiring or Connector 🟡 Medium Probability The wiring harness that passes through the rubber boot in the driver's door jamb is a very common failure point on Ram trucks. Constant flexing from opening and closing the door can break the small wires for the sensor. Owners on forums report finding multiple wires completely severed inside this boot.
   How to confirm: Visually inspect the wiring inside the door jamb boot for breaks or chafing. This may require pulling the boot away from the body and door. 🎬 See how to find and repair broken wires in the door jamb. Also, check the sensor's connector for corrosion, moisture, or pushed-out pins. TSB S2208000080 specifically directs technicians to inspect the G31 and G931 circuits between the mirror, Driver Door Module, and Body Control Module.
   Typical fix: Repair the broken wire(s). The best practice is to solder in a new section of wire and protect it with heat-shrink tubing to maintain flexibility, as simple butt connectors can be too rigid for this location. The main harness connector may need to be unplugged from inside the cab to get enough slack to work.
   Est. part cost: $5-$25
3. Incorrect Aftermarket Mirrors ⚪ Low Probability When owners install aftermarket tow mirrors, they sometimes choose models that do not include a provision for the AAT sensor, use an incompatible one, or forget to plug it in. Some owners report that cheap aftermarket sensors are not calibrated correctly and can trigger high/low temp codes (like P0073) when parked in the sun.
   How to confirm: Determine if the truck has aftermarket mirrors. If so, verify with the mirror manufacturer if they are equipped with the correct AAT sensor. If the sensor is missing, a dedicated harness may be needed.
   Typical fix: Replace the mirrors with a compatible set that includes the AAT sensor. Alternatively, for some aftermarket mirrors, a separate AAT sensor harness kit (like those from Boost Auto Parts) can be purchased and wired into the mirror's main connector.
   Est. part cost: $25-$800

Rare But Worth Checking

• Faulty Powertrain Control Module (PCM) or Body Control Module (BCM): This is extremely rare. The PCM/BCM should only be considered as the cause after all other possibilities, including the sensor and all related wiring between the sensor, DDM, and BCM, have been thoroughly tested and ruled out.
• Blown Fuse: While less common than a wiring break, a blown fuse can cause the circuit to fail. On 4th generation trucks, owners have identified fuse #99 (10A) in the main engine bay fuse box 🎬 Watch: How to check the temperature sensor fuse on your Ram. as being related to the temperature sensor circuits. This is a quick and easy check to perform early in the diagnosis.

Diagnosis Steps

1. Read the fault codes with an OBD-II scanner to confirm P0070 is present.
2. Check the outside temperature reading on the dashboard. If it shows an impossible value like -40°F or is blank, it strongly points to an AAT circuit issue.
3. As a quick first step, check fuse #99 (10A) in the main fuse box under the hood (primarily for 4th gen models).
4. Visually inspect the AAT sensor. On most 2016-2023 Ram 1500s, it's a small nub on the bottom of the driver's side mirror. Look for physical damage.
5. Carefully pull back the rubber boot between the driver's door and the body and inspect the wires for any breaks, chafing, or damage. This is a very common failure point.
6. If wiring looks good, inspect the sensor's electrical connector for corrosion, backed-out pins, or moisture.
7. If no obvious damage is found, use a multimeter to test the sensor's resistance. If it's open, shorted, or doesn't match expected values for the current temperature, the sensor is likely bad.
8. If the sensor tests good, follow the diagnostic path from TSB S2208000080: check for continuity and voltage on the G31 and G931 circuits from the AAT sensor connector to the Driver Door Module (DDM) and from the DDM to the Body Control Module (BCM).
9. After performing a repair (replacing sensor or fixing wiring), clear the codes. Per TSB S2208000080, you must drive the vehicle for at least 5 minutes at a speed above 15 mph to allow the BCM to update the temperature reading before the code can be successfully cleared.

Parts You'll Likely Need

• Ambient Air Temperature Sensor (OEM #68457701AA (supersedes 68138681AB, 68138681AC, 68138681AD, 68138681AE)) — This is the most common component to fail for this code, either due to internal failure or physical damage.
  Trusted brands: Mopar, Dorman, Standard Motor Products
  OEM price range: $25-$50
  Aftermarket price range: $15-$30
• Wire Repair Supplies — If the cause is broken wires in the door jamb, you will need automotive-grade wire, solder, and heat-shrink tubing to perform a durable repair.
  Aftermarket price range: $5-$20

Related Codes That Often Appear With This One

• P0073 — This code for 'Ambient Air Temperature Sensor Circuit High' is often seen with P0070. Both are cited in the same Technical Service Bulletin (S2208000080) and point to a fault in the same circuit, often a broken wire or open circuit.
• P0071 — Indicates an 'Ambient Air Temperature Sensor Range/Performance' issue. It can appear if the sensor is providing erratic or illogical readings, such as from a poor quality aftermarket sensor or intermittent wiring connection.
• P0072 — This code for 'Ambient Air Temperature Sensor Circuit Low' points to a short to ground in the circuit, whereas P0070 is a more general circuit fault.

Technical Service Bulletins (TSBs) & Recalls

• S2208000080: Addresses an ambient

Platform-Specific Known Issues

• TSB S2208000080 - Specific Wiring Inspection Path: This Technical Service Bulletin directly addresses P0070 and P0073. It instructs technicians to inspect the G31 & G931 circuits from the AAT sensor in the mirror, to the Driver Door Module (DDM) C2 connector, and then from the DDM C4 connector to the Body Control Module (BCM) C4 connector. It also specifies a required drive cycle (5 mins > 15 mph) to update the sensor reading after a repair.
• Owner 'Sensor Reset' Trick: Some owners on forums have reported temporarily fixing a stuck temperature reading by turning the truck off, unplugging the AAT sensor, turning the ignition on (the display may show an extreme value), turning it off again, and plugging the sensor back in. This may reset the reading, but does not fix the underlying cause if one exists.

Mechanic-Grade Diagnostic Values

• Ambient Air Temperature Sensor Resistance — expected: Varies with temperature. A detailed chart shows values like 100,260 Ohms at -5°F, 40,153 Ohms at 25°F, 10,449 Ohms at 75°F, and 5,774 Ohms at 100°F. A common rule of thumb is ~10 kOhms at room temperature.. Failure: Resistance is near zero (shorted) or infinite/OL (open circuit). A reading that doesn't correlate with the actual ambient temperature indicates a faulty sensor.
• AAT Sensor Circuit Voltage (at sensor connector) — expected: Approximately 5.0 Volts DC between the two pins of the sensor connector with the sensor unplugged and ignition on.. Failure: Significantly less than 5.0V or 0V indicates an open or short in the wiring leading from the BCM/DDM.
• AAT Sensor Voltage (Live Data on Scan Tool) — expected: The voltage should be between 0.1V (hot) and 5.0V (cold). A diagnostic document notes that a voltage greater than 4.98V will set a high-input code like P0073.. Failure: A voltage stuck at or near 0V or 5V indicates a short or open in the circuit.

Scan Tool Commands That Help

• AlfaOBD / witech: Read BCM/PCM Fault Codes — Used to confirm the presence of P0070 and related codes like P0071, P0072, P0073. This is the first step in any diagnosis.
• AlfaOBD / witech: Clear Fault Codes — Used after a repair is completed. For the AAT sensor, the TSB specifies that the vehicle must be driven for 5 minutes at over 15 mph before the code can be successfully cleared.
• AlfaOBD: Body Control Module (BCM) Active Diagnostics — While there isn't a specific 'AAT reset' command, advanced tools like AlfaOBD allow users to connect directly to the BCM to monitor live data from the sensor and perform system resets, which can help verify if the BCM is receiving the signal correctly after a repair.

Wiring & Ground Locations

• G31 (AAT Signal) — This is the signal wire for the AAT sensor. It runs from the sensor in the driver's mirror, through the door jamb boot, to the Driver Door Module (DDM), and then to the Body Control Module (BCM). It lands on Pin 22 of the BCM C4 connector. The wire color is typically Violet/Light Green.. This is the primary signal circuit. An open or short on this wire is a direct cause for P0070 and related codes. The TSB specifically calls for its inspection.
• G931 (Sensor Ground) — This is the sensor ground wire. It follows the same path as G31 and lands on Pin 23 of the BCM C4 connector. The wire color is typically Violet/Brown.. An open in the ground circuit will cause the sensor to read incorrectly or not at all, leading to a fault code.
• Driver Door Jamb Boot — The flexible rubber boot between the driver's door and the truck's A-pillar.. This is the most common location for wire breakage due to the constant flexing from opening and closing the door. Both the G31 and G931 circuits pass through this boot and are highly susceptible to damage here.
• BCM C4 Connector — The Body Control Module (BCM) is typically located in the cabin, often behind the driver's side lower dashboard or kick panel. C4 is a specific multi-pin connector on the BCM.. This is the termination point for the AAT sensor circuits. Testing for continuity and voltage at pins 22 (G31) and 23 (G931) can confirm if the signal is reaching the BCM, helping to isolate the fault to the wiring or the module itself.

Real Owner Repair Stories

• RamForum.com user post (2002 Dodge Ram Quadcab (similar 4th gen issue)) — Door speaker, dome light, and door lock not working.
  ❌ Tried (didn't work) Initial inspection without checking inside the door boot.
  ✅ What actually fixed it The owner slit open the rubber boot in the door jamb and found 5 completely severed wires and 2 more with broken conductors inside the insulation. The fix was to disconnect the main harness plug from the body side (by removing interior plastic panels) to get slack, then solder in new sections of wire for all the broken circuits.
• YouTube video by Boost Auto Parts (2019+ Ram 1500 (5th Gen)) — Check Engine Light (often P0073) after installing aftermarket tow mirrors that lack an AAT sensor.
  ❌ Tried (didn't work) Clearing the code without addressing the missing sensor.
  ✅ What actually fixed it Installing a dedicated AAT sensor harness. The black wire from the new harness was inserted into position 6 (top left) and the white wire into position 1 (bottom left) of the white mirror connector. The new sensor was then plugged into the harness.

Model Year Variations Within This Range

• 2019-2023 (5th Gen) vs 2016-2018 (4th Gen): While the AAT sensor is in the driver's mirror on most trucks in this range, the introduction of the 'Classic' model (a 4th gen body style sold alongside the new 5th gen) from 2019 onwards can cause confusion. A 2019 'Warlock' is a 4th gen Classic, while a 2019 'Laramie' is a 5th gen. The physical mirror housings and some internal wiring connectors (like the one for adding an aftermarket sensor) can differ between the two generations, making it crucial to identify the correct generation before ordering parts or consulting wiring diagrams.