The exact same thing happened to me but actually as i drove it off the lot. I took it to the dealer and thye said it was the ABS encoder or something like that. It is not dangerous however your anti-lock barakes may not kick in. what this means is that on slipery roads if you press the breaks had they may lock, other than that you will not notice a difference at all and it will not damage anythin else.
You may have to wait for a part to be ordered and at that time which was march 06 they were on backorder, i was told it was a common problem. I drove mine for 500 miles while waiting for the part.
If you wana be sure if you have the same problem before you get to the dealer, while the message is on the DIC press the blue onstar button and tell them about the message and ask them whats wrong. They can run a remote diagnostic while you are driving or parked and will tell you. Thats how i found out what the problem was before the dealer told me.
Dont worry about it, its a minor problem, easy fix! Enjoy your truck!
