5.0Screw22

I recently bought a used 2019 F150 Lariat to use as a winter vehicle. I have noticed that my outside air temperature reading is off by as much as 12 degrees. The reported temp on the Sync screen goes up and down, but it is not correct. I attempted a couple of reset procedures that I found online (holding buttons on the climate controls panel, etc.) but they did nothing to correct the problem. So, I decided to remove the sensor from the bottom of my RH mirror. I thought disconnecting the sensor might force the system to fault and then reset when I reinstalled the sensor. Oddly enough, removing the sensor did not cause the system to report a fault. In fact, it continues to provide outside temperatures, and they are still incorrect. I have run the truck with the sensor removed for over a day and the system is still reporting varying incorrect temperature readings. I have also scanned for trouble codes with Forscan and I have no DTCs related to this problem. Does anyone have any experience with this situation?

Bluegrass

The outside Temp Sensor needs to be reasonably accurate and stable because the PCM program uses it along with the cylinder head temp Sensor reading to make starting program decisions.
Good luck.

5.0Screw22

So how does the system report an outside temperature when there is no sensor in place? I think I saw a default value somehwere that the system presents when the sensor fails, but I have a reading that is varying so I am guessing that it is determining the temperature in a different way. Right now, the outside temp is 48 and the Sync screen is displaying 56 with no temp sensor installed.

djfllmn

iTrader: (1)

what happens if you unplug the entire mirror?

Wicked ace

That sensor location was moved mid model year 2018. In all probability the wiring & plug is still in place for the previous location behind the front grill. Look to see if a sensor was installed there..

Bluegrass

The reason it was moved was the location it was in was due to being shaded, engine heat and better accounting for Sun heating effects.
It's in Ford Doc description. Can't use two Sensors in or near the engine bay for the same purpose or outside reading.
Take a look in Ford OBDII Overview for 2021 Gas engine and the page on Ambient Sensor location and use.
Most think the sensor is just for outside temp display, but it's used by the PCM as a check against the engine sensor reading, at that time, for Logic decisions on fuel injection pulse widths etc for starting.
Some report longer cranking time is very cold temps. This is part of it.
ETH in fuel can lengthen the crank time to starting. Afterall, it's a cooling agent.
Good luck.

SpencerPJ

Mine is only fairly accurate in the early day. Once out in the sun, it varies as well, 10 degrees. Pretty disappointing, but when I need outside temp, I just ask Siri.

5.0Screw22

Yes, this sensor is tied to a long list of systems in the vehicle. I believe it also affects remote start functions, the active shutters, the climate control system, AS/S, and many other systems. That is why it is important to make sure it is working properly. So much of this vehicle relies on the information from this sensor. If it was just outside temp, it would not be a big deal. I believe I read somewhere that the acceptable deviation is =/- 3 degrees F.

So, after leaving my sensor disconnected for over a day, I reinstalled it. So far, the sensor is providing a accurate reading again. I still cannot explain how the system was able to display varying readings with no sensor installed. Only time will tell if the sensor is actually working properly. If the issue returns, I may swap the sensor from my 22 and see if that fixes it. I see they both use the same part for the temp sensor in the mirror. If I have to do more to address this issue, I will update this post to help others with the same issue.

5.0Screw22

Just a quick update... Changing the sensor has not fully corrected the issue. While the sensor results are a little more accurate, at times they still are way off for no reason. It seems like the longer the truck operates the less accurate the readings become? The other day I drove to the store and the temp was reading was about 44 degrees F. It was reading within 1 or 2 degrees of actual, which I consider acceptable. It was a cool, dreary day with light rain and no sun. I was in the store for less than 15 minutes but when I restarted the truck, it was reporting the temp 10 degrees higher (54 degrees F) than when I shut off the truck. The outside temp was exactly the same, the conditions had not changed at all. This kind of shift does not make sense for a mirror mounted sensor, especially in cooler weather with no sun.

Taggart

How are you measuring the ambient temperature at the truck's location? The sensor (and your other temperature measurement) can be affected by other factors. These factors are usually more significant when the truck is sitting still, and less significant when the truck is in motion and has airflow across the sensor.