Its your wheel bearing. You may have noticed a hum while driving over 35 that changes when you rock the steering back and forth. A while after this the lights come on as the sensor is part of the hub assm.
I just got back from my dealer today they knew right off what it was though they chose to say it was bad wiring instead of bad bearing. And they only changed the one that threw the code though both were noisy. I have to go to the brake guy to look at the rotors and Ill have him double check the other bearing.
In your situation I would call gm and then have them refer you to another dealer and report the one you went to.
Someone had posted somewhere else about getting customer survey cards and sending them in and how hard it is to get them from the dealer...the one I go to staples them directly to the ticket and will follow up if you dont send them in. I still hate dealers and only go in for warranty work I have a real mech for the rest.
As far as driving your car its ok to drive till you can get it in. The light may go away but will come back by rocking steering while driving at 35mpi.
And if you look around a bit the bearing thing is a common issue join the club
