Do a search on the topic. I think someone had determined it's caused by a bad diode in the clock - but unless you are savvy with electronic repairs you might not be able to repair it.
My clock went bad under warranty and they replaced the clock. It was like pulling teeth to get the dealer to do it, but persistence pays.
If it's not worth the effort, put a piece of black electrical tape over it. Fortunately the car will run the same with or without the dumb clock.![]()