Exclamation point and beeping when putting car in reverse

Hi,

This morning I put the car in reverse and got a display on the dash that showed the birds-eye view of the car with an exclamation point in front of it, accompanied by a short series of beeps. The car operated just fine and I was able to drive into work. This only happens in reverse.

The display was the one that shows up on the dash when your parking proximity sensors are going off - it showed the picture of the car, as done with the proximity sensors, but instead of showing a side where the sensor detected a close object as is done with the proximity sensors, it just showed the car with an exclamation point in the front of the car (should have taken a picture, will do so later if needed). This was not the TPMS warning (I've had that before, this is definitely different). Again, this only happens when I put the car in reverse. I turned the car off and started it again, and that did not clear the warning.

I'm wondering if maybe there's an issue with one of the sensors. I looked through the manual but didn't see this warning shown in the manual anywhere.

Has anyone seen this before?

Simply DUST on radar detector.

Very common for me ... the last alert of this is a drop of frozen water on 1 detector (this disable all detectors).
It's happened only once.

Surprisly, I have frosty damp fog on this day and this is not a problem for radars when they are frozen (to detect correctly the distance).

Maybe this...
It happened to me a few weeks back, never saw it again.

Yep, that picture looks just like what I saw, only the exclamation mark was positioned on the front of the car. Ice or dust on the sensors makes sense. We had our first blast of icy / snowy weather here this morning, so I'm guessing it was ice. I'll clear the sensors when I get back to the car later today.

Thanks very much for the replies - sets my mind at ease!