2019 Ambient Air Temperature Sensor Issue
10-30-2023, 03:31 PM
#11
The outside Sensor is connected to the PCM internally.
There may be a cabling/connection, connector issue or even at the PCM internal board location.
It appears the issue itself is temperature sensitive at the fault location causing the readings to vary in such a manner.
On my vehicle, the temperatures of coolant sensor, transmission etc after a night setting are all either the same or within 1*.
These reading are not from the common dash display but using a Scanner to look at the individual sensors.
Also, in Dash Engineering Mode, the readings are in C*. Converted to F*, they all read the same as a check on the Scanner readings.
As the engine heats, all the sensors begin to vary their reading levels per their applications.
.
Not a part of your issue; I can even see the Cat temps rise to over 1000* then slowly cool back to the 800 to 900* ranges as they are supposed to do from a cold start to full end operating temperature, both banks. Same for fuel pressure that begins at about 65 psi and can go as high as 3000+ psi, lower and vary as needed for direct fuel injection.
Barometric pressure and Temp readings and changes from the MAP Sensor cold and running. Both Temp reading inside and out agree when cold soaked overnight, before starting.
In a way, these vehicles have an internal Scanner to look at a lot of operating systems parameters on board.
The minor problem is you have to convert many readings to recognizable Decimal numbers to be useful. Some readings are in Decimal, some in Hex and some in Octal number display.
Good luck.
There may be a cabling/connection, connector issue or even at the PCM internal board location.
It appears the issue itself is temperature sensitive at the fault location causing the readings to vary in such a manner.
On my vehicle, the temperatures of coolant sensor, transmission etc after a night setting are all either the same or within 1*.
These reading are not from the common dash display but using a Scanner to look at the individual sensors.
Also, in Dash Engineering Mode, the readings are in C*. Converted to F*, they all read the same as a check on the Scanner readings.
As the engine heats, all the sensors begin to vary their reading levels per their applications.
.
Not a part of your issue; I can even see the Cat temps rise to over 1000* then slowly cool back to the 800 to 900* ranges as they are supposed to do from a cold start to full end operating temperature, both banks. Same for fuel pressure that begins at about 65 psi and can go as high as 3000+ psi, lower and vary as needed for direct fuel injection.
Barometric pressure and Temp readings and changes from the MAP Sensor cold and running. Both Temp reading inside and out agree when cold soaked overnight, before starting.
In a way, these vehicles have an internal Scanner to look at a lot of operating systems parameters on board.
The minor problem is you have to convert many readings to recognizable Decimal numbers to be useful. Some readings are in Decimal, some in Hex and some in Octal number display.
Good luck.
Last edited by Bluegrass; 10-30-2023 at 03:36 PM.
10-30-2023, 03:44 PM
#12
Member
Thread Starter
Taggart: I understand what you are saying, but this is not typical of any of the similar Ford trucks I have owned, including a 2018 Platinum, 2019 Limited and a 2022 Platinum. None of those had (or have) this problem. My 2022 is accurate all of the time, that's why I used the sensor from it for testing purposes. During the 15 minute drive home, the temp never went down at all. It stayed at 54 the entire drive home and it had plenty of air flow at 55mph. There is something else causing this issue.
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Taggart (10-30-2023)
10-30-2023, 03:54 PM
#13
Member
Thread Starter
The outside Sensor is connected to the PCM internally.
There may be a cabling/connection, connector issue or even at the PCM internal board location.
It appears the issue itself is temperature sensitive at the fault location causing the readings to vary in such a manner.
On my vehicle, the temperatures of coolant sensor, transmission etc after a night setting are all either the same or within 1*.
These reading are not from the common dash display but using a Scanner to look at the individual sensors.
Also, in Dash Engineering Mode, the readings are in C*. Converted to F*, they all read the same as a check on the Scanner readings.
As the engine heats, all the sensors begin to vary their reading levels per their applications.
.
Not a part of your issue; I can even see the Cat temps rise to over 1000* then slowly cool back to the 800 to 900* ranges as they are supposed to do from a cold start to full end operating temperature, both banks. Same for fuel pressure that begins at about 65 psi and can go as high as 3000+ psi, lower and vary as needed for direct fuel injection.
Barometric pressure and Temp readings and changes from the MAP Sensor cold and running. Both Temp reading inside and out agree when cold soaked overnight, before starting.
In a way, these vehicles have an internal Scanner to look at a lot of operating systems parameters on board.
The minor problem is you have to convert many readings to recognizable Decimal numbers to be useful. Some readings are in Decimal, some in Hex and some in Octal number display.
Good luck.
There may be a cabling/connection, connector issue or even at the PCM internal board location.
It appears the issue itself is temperature sensitive at the fault location causing the readings to vary in such a manner.
On my vehicle, the temperatures of coolant sensor, transmission etc after a night setting are all either the same or within 1*.
These reading are not from the common dash display but using a Scanner to look at the individual sensors.
Also, in Dash Engineering Mode, the readings are in C*. Converted to F*, they all read the same as a check on the Scanner readings.
As the engine heats, all the sensors begin to vary their reading levels per their applications.
.
Not a part of your issue; I can even see the Cat temps rise to over 1000* then slowly cool back to the 800 to 900* ranges as they are supposed to do from a cold start to full end operating temperature, both banks. Same for fuel pressure that begins at about 65 psi and can go as high as 3000+ psi, lower and vary as needed for direct fuel injection.
Barometric pressure and Temp readings and changes from the MAP Sensor cold and running. Both Temp reading inside and out agree when cold soaked overnight, before starting.
In a way, these vehicles have an internal Scanner to look at a lot of operating systems parameters on board.
The minor problem is you have to convert many readings to recognizable Decimal numbers to be useful. Some readings are in Decimal, some in Hex and some in Octal number display.
Good luck.
10-30-2023, 05:28 PM
#14
Senior Member
An AAT reading of:
- 44°F is a signal voltage of 3.87 V.
- 54°F is a signal voltage of 3.64 V.
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5.0Screw22 (10-31-2023)
10-30-2023, 06:04 PM
#16
Senior Member
I would start with the main door connector C610.
10-30-2023, 11:38 PM
#17
Senior Member
I believe that the AAT sensor "reports" directly to the PCM which then shares the value with other modules as needed via network communication. Do you have access to read actual AAT value at the PCM? While doing so, start wiggle testing. Tap on the mirror, open and close the door a few times, wiggle wires that you can easily access, etc. It baffles me why an unplugged sensor would read at all. A long shot, but you don't happen to have a sensor in the old location as well do you?
I'm guessing that many people would suggest ignoring it since it isn't affecting anything. But 10 degrees off would drive the OCD part of me wacky!
I'm guessing that many people would suggest ignoring it since it isn't affecting anything. But 10 degrees off would drive the OCD part of me wacky!
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?
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?
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5.0Screw22 (10-31-2023)
10-31-2023, 11:42 AM
#18
Senior Member
FORScan can monitor AAT signal voltage to the PCM by monitoring PCM PID AAT_V.
10-31-2023, 11:51 AM
#19
Member
Thread Starter
Thank you all for your suggestions. Yes, this is not good for OCD people like me! Last night I left the truck outside. This morning, it was 27 outside with light snow. I had a little snow and frost on top of the mirror cap and it was reporting the outside temp as 42 degrees. 
I need to see if I can view the temp in the PCM with any of my scanners or software. I have never had a need to view it, so I really do not know if I have that ability. If I can do a wiggle test, that is part of my plan. That said, I am wondering if you can do a wiggle test on this sensor. It is my understanding that the system may only reads that data periodically. If that is the case, then a wiggle test may not work. I will also disconnect and clean all of the connections with contact cleaner to see if that helps.
I can see that the door harness is probably not original to this truck. When I pulled the mirror cover on the inside of the door, I noticed the harness has a connector for a camera, but this truck did not come with that option. I checked and that connector is not present in the driver's side door harness. I suspect that the passenger harness may have been replaced. If someone used a harness from a salvage yard, the odds of corrosion on connectors could be more likely in my mind.
I suspect I may have more than one issue and this is why: I have noticed that the temperature reported seems to rise as the vehicle heats. I am wondering if heat from the interior is passing into the mirror and affecting the temp. I know there is a block of foam installed in the base of the mirror and another one between the mirror base and the door shell. Maybe one of them is out of place and allowing heat to pass into the mirror? I do not think this is the entire problem, but it may be contributing. When I pull the mirror, I will make sure that both foam rubber seals are in place. This would not address the fact that the system still provides reading without the sensor in place. That seems more like an issue in the wiring.
I need to see if I can view the temp in the PCM with any of my scanners or software. I have never had a need to view it, so I really do not know if I have that ability. If I can do a wiggle test, that is part of my plan. That said, I am wondering if you can do a wiggle test on this sensor. It is my understanding that the system may only reads that data periodically. If that is the case, then a wiggle test may not work. I will also disconnect and clean all of the connections with contact cleaner to see if that helps.
I can see that the door harness is probably not original to this truck. When I pulled the mirror cover on the inside of the door, I noticed the harness has a connector for a camera, but this truck did not come with that option. I checked and that connector is not present in the driver's side door harness. I suspect that the passenger harness may have been replaced. If someone used a harness from a salvage yard, the odds of corrosion on connectors could be more likely in my mind.
I suspect I may have more than one issue and this is why: I have noticed that the temperature reported seems to rise as the vehicle heats. I am wondering if heat from the interior is passing into the mirror and affecting the temp. I know there is a block of foam installed in the base of the mirror and another one between the mirror base and the door shell. Maybe one of them is out of place and allowing heat to pass into the mirror? I do not think this is the entire problem, but it may be contributing. When I pull the mirror, I will make sure that both foam rubber seals are in place. This would not address the fact that the system still provides reading without the sensor in place. That seems more like an issue in the wiring.
10-31-2023, 12:22 PM
#20
Senior Member
The PCM sends raw ambient air temperature data to the FCIM. The FCIM filters the raw data, sends it to the APIM and the touchscreen displays the outside temperature. For this reason, you can't meaningfully perform a "wiggle" test unless you are actually monitoring the AAT signal output.
The WSM also lists the following as possible causes of an inaccurate outside temperature display:
The following is from the WSM:
The Ambient Air Temperature (AAT) sensor is hardwired to the PCM through separate input and return circuits. The PCM provides a reference voltage to the Ambient Air Temperature (AAT) sensor and monitors the change in voltage resulting from changes in resistance as determined by outside air temperature. The PCM sends the ambient air temperature message to the GWM through the HSCAN1. The GWM sends the air ambient temperature message to the FCIM over the MS-CAN.
The PCM is programmed to update the messaged outside temperature data at different rates depending on several criteria to prevent false temperature displays due to a condition known as heat soaking. Heat soaking is where the outside air temperature is hotter in the location of the Ambient Air Temperature (AAT) sensor than the actual outside air temperature.
When the sensed outside temperature rises, the display updates slowly at varying rates based on vehicle speed. When the sensed outside temperature drops, the display updates more quickly following the drop experienced by the Ambient Air Temperature (AAT) sensor.
If the ambient air temperature filtered message is missing or invalid for 5 seconds or more from the PCM, the FCIM displays all dashes (- -) in the outside air temperature display area.
If the air ambient temperature filtered message is missing or invalid for less than 5 seconds, the touchscreen defaults the outside air temperature display to the last temperature reading, based upon the last message received.
The WSM also lists the following as possible causes of an inaccurate outside temperature display:
- Communication concern
- AAT sensor
- GWM concern
- PCM concern
- FCIM concern
The following is from the WSM:
The Ambient Air Temperature (AAT) sensor is hardwired to the PCM through separate input and return circuits. The PCM provides a reference voltage to the Ambient Air Temperature (AAT) sensor and monitors the change in voltage resulting from changes in resistance as determined by outside air temperature. The PCM sends the ambient air temperature message to the GWM through the HSCAN1. The GWM sends the air ambient temperature message to the FCIM over the MS-CAN.
The PCM is programmed to update the messaged outside temperature data at different rates depending on several criteria to prevent false temperature displays due to a condition known as heat soaking. Heat soaking is where the outside air temperature is hotter in the location of the Ambient Air Temperature (AAT) sensor than the actual outside air temperature.
When the sensed outside temperature rises, the display updates slowly at varying rates based on vehicle speed. When the sensed outside temperature drops, the display updates more quickly following the drop experienced by the Ambient Air Temperature (AAT) sensor.
If the ambient air temperature filtered message is missing or invalid for 5 seconds or more from the PCM, the FCIM displays all dashes (- -) in the outside air temperature display area.
If the air ambient temperature filtered message is missing or invalid for less than 5 seconds, the touchscreen defaults the outside air temperature display to the last temperature reading, based upon the last message received.
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5.0Screw22 (10-31-2023)