Washed my truck yesterday. 2018 XLT Screw. It's winter temps here but had warmed up enough for a wash. Today every time I go into reverse my back up proximity is beeping constant. Where exactly is the sensor? Maybe I can put a hair dryer on it for a bit.

 

there are a total of 4 of them in the back bumper.

 

They are the 4 round "buttons" in the back bumper. One of them probably has a bit of ice on it.

 

I'll have a look. Maybe blocked by ice or snow.

 

Check the connector for water intrusion

 

2018 130,000 km. I’ve had that happen after washes. Water intrusion most likely.

 

What's the fix? A little dielectric grease?

 

Good question. Mine simply started working after it dried out a couple days later. Maybe the dielectric grease like you said or a hot air gun?

Also I was never sure which sensor was the problem.

 

People who have reported having that problem, recommended dielectric grease. Should keep the moisture out of the connector, if that's the problem.

 

Dielectric grease helps but doesn't always solve it. I did all my connectors and still have issues here or there.