If the TrailBlazer could tell you what the actual problem is through the D.I.C, that would be cool. However, I don't think that it does....
If you still have Onstar activated, you can hit your button & ask them to do an on board diagnostic check for you. They can give you the code of the problem(s) & then you can call up your local dealer & ask there if Onstar doesn't know the exact problem.
Another thing that could cause that light to turn on & silly enough to say so....but try turning your gas cap a few more times (3x's at least)
By doing so, it seals the ????? better & it won't trigger the CEL to pop up on you. Hopefully, that's all it is.....check it out & see
