Script Errors are usually caused by voltage drops, be sure you have removed all the fuses for the On Star, Stereo etc... that the manual says to remove, and that you do not have any accessories running while you are programming the truck. If you still get a Script Error your battery might need to ...

I cannot modify the performance tune on my 2003 Silverado. After making changes, I get a message saying - Please Wait...communicating. The text then changes from "communicating" to "writing", then abruptly fails, with the message: Data Uploading - UNKNOWN ERROR. When I press any key, I get another ...