CObus is right. If there is welding to be done at the very least all the connections to sensitive stuff like the DDEC and ATEC computers need to be disconnected. If there are any house computers they need to be protected by disconnecting them as well.

Welding on our buses is not rare. As can be seen repairs often need weldiing, but Prevost often has recalls where the fix requires welding. The most common reason for a welder to be used is if one of the inner drive axle wheel studs breaks and the tool to remove it fails to work. Then the only alternative is to weld a nut on the end of the stud so it can be removed using the impact wrench.

Welding is OK, but precautions need to be taken.

Removing the battery ground may be how some would do it, but I have removed the power connectors at all electroninc devices so there is no connection between those devices and the chassis. It is more troublesome, but on those occasions when I have welded on my bus I have had no problems.