I noticed after I washed my 2010 RX that the external air temperature reading is wrong. anyone had this problem, where is sensor located?

 

That happens every time I wash my car but it corrects itself when it dries. Yours stayed cooler?

 

On other Lexus' the sensor is behind the front bumper. It is normal for it to read low after a wash, evidently water runs down inside the grill opening and hits the sensor or puddles around it. You just have to wait for it to evaporate.

 

live in Phoenix area and outside temperature is 100 deg + and temp on dash is showing 77 deg. In the past this has alway corrected it self after car wash and car dried out

 

Is there a way to change the units from farenheit to Celsius ?

 

The water being used is most likely cold. It will lower the outside reading for a little while until the sensor re-adjusts.