It's called the "Ambient Temp Sensor" with part number (I believed to be) 88790-06020. It is located behind the front grill (not sure if it can be seen through the front grill for your year or hiding behin the bumper cover, perhaps access able from the engine compartment with the hood open and Sight Shield removed..), attached near the radiator support bracket...
EDIT: With my 2016, the sensor is located in the center behind the grill (space between the grill and the radiator, just lower than the Toyota emblem attached on the center support).

You may want to search the Web/online Toyota catalog (or YouTube) using the name & part number provided above to have a look at the diagram for exact 2019 model location.

P.S. I don't believe those sensors can be cleaned, however, I thought the temp reading may be adjusted to compensated such error affected by the heat radiated from engine... I am not sure how, but I will keep looking and update here if I find for it.

 

I thought the temp reading may be adjusted to compensated such error affected by the heat radiated from engine..

The heat radiating from the engine is usually displaced after the vehicle is moving. The air and/or engine fan helps to keep the engine heat away from sensor. During the summer days when park the truck after a drive...then start the HL about 5 minutes later..the outside temp reading is usually 10+ degrees hotter then it really is. Once I get moving the temps start to come done. In a few miles the outside temp is as accurate as it gets - usually 2-3 degrees within what is reported by local weather or weather app on iphone and Apple Watch.

 

Thanks for your answers guys...MikeinNH says 2 to 3 degrees from local reporting....that's about what mine is, but I think if they did it right on my 2008, they should have it right on my 2019. It just seems tacky

 

A couple weeks ago I adjusted the ambient air temp reading -2 degrees C with Carista. Reads pretty much right on now compared to periodic checks of the temperature on The Weather Channel.

 

Good to know! If there is that such parameter adjustable through Carista, that parameter must be also available through Techstream.