Stabilitrac engaged message HELP!

Greetings,
I have a 2004 CTS with the 3.6 VVT and PDX. My car is totally bone stock with no modifications. Intermittently the DIC says that the stabilitrac engaged. It usually occurs as I am gently driving on a straight hwy at normal hwy speeds. There is no rain,spit, or bird crap on the road either.
Just this morning it happened when I let up on the gas. I took it to the dealership 4 weeks ago and they hooked up the scanner to the car and got no codes they then drove it and could not duplicate the problem and of course charged me $90 to tell me that. I am thinking that it is a bad accelerometer or wiring. Any help or advise would be greatly appreciated.