It may sound dumb but check your switches and make sure your cables are hooked up correctly. It took me way too long one time to realize my stinger was hooked to the cc stud and ground to the cv stud not the work stud. Just a thought.

I had the same problem with my trailblazer(same engine),and it was a fuse,check the owners manual,and you'll see it.

The fuse was white like ceramic,I got one from an appliance store,its been good ever since.

Miller has an awesome product support, my module for same type of welder was bad and after an e-mail to miller, I had the info needed to trouble shoot and ordered new module, case closed. (high Idle would not kick down)