Mine did something similar, cleaning did nothing. Ended up ordering a new unit for $49 shipped from GMPartsStore under part# 13540010. Could I have warrantied it? Sure, but just as easy to order it myself and swap out on my own in 5 minutes.
Same issue here. Dealership replaced it the first time at 7K, I have 14K on it now and it's done the same thing. I keep it garaged and clean. i'll keep taking it back, 50K warranty on it. It's a pain to take it in. i wish it was just a matter of cleaning. images of both.
Mine is doing same thing, going in in a week for it. Guessing will be a replace!
GM should put more care in stuff like this; that is their BRAND....nice touch on the car, but lame if it fades away. You make a good point though, I should photograph it, as it only comes on in the dark.