i have a 99 LT, when i bought it the check engine light came on, come to find out it was the vaccum hose that connects to the left inner fender. When i took it to the shop the scan tool couldnt connect to it. I then took it to another shop there scan did the same thing. what do you think it is.

 

Is your cigarette lighter working? The DLC is powered off of the same circuit as the cigarette lighter. If the fuse blows for whatever reason, a scan tool will not be able to connect with the vehicle.