What is the red flashing light in the back of my 2002 rendezvous

yeah its in the back on the ceiling of the cargo area

no there is a little thing that has 3 lights and there is just 1 flashing red

it is your ultrasonic rear park assist- when it works normally, it would light 2 orange lights before the red one comes on- when the red comes on you shouldn't back up any farther or you will hit the object behind you- if it stays flashing all the time you either have a problem with the assist, or if you have a receiver hitch in the back, take the end with the ball out of it and see if it stops flashing. I hope this helps.

I have a 2002 Buick Rendezvous and my light that's on the dash that blinks red and is not blinking no more I think there's some thing wrong my alarm cause now after I bought this vehicle in September it has not worked sense. Could someone help me?