I've welded a bunch of stuff on vehicles. I've never disconnected a module or battery, and I've never had a problem with electronics. What you need to make sure you do is connect the ground to the piece you are welding. In other words, if you are welding the frame, ground the frame, if you are welding the body, ground the body, if you are welding the exhaust, ground the exhaust. Where you run into issues is if the current has to travel through something to complete the circuit. So if you ground to the frame and weld the exhaust, the current has to travel through something to complete the circuit to weld, and that can cause electrical surges that can kill modules if it hits it just right.