stabilitrac lights

Okay, so I bought my wife a sweet 06 Envoy denali with the 5.3L motor and all the bells and whistles. I love it, its perfect. Here is just a quick question. It has 94000 miles and we bought it from a reputable dealer in town. What should be my list of check offs to make sure i have done on it...

I have read this and other forums on the P2135 issues. I had other codes too and following the helpfull posts of this Forum I have eliminated all but the P2315 and just in the last 2 days I am getting the Stabilitrac lights on also. I have sent my PCM out for reprograming, engine does run...