gauge cluster circuit board- delay timing solid state relay- when they start to go south all kinds of weird things happen. Not limited to gm industry wide. and yep like eveyone else has mentioned grounds- but one has to remember that the computer systems operate on their own circuits not chassis ground. All components have constant supply voltage on one side, the other side is switched ( you can call it the negative leg if you want) by the computer or various relay/ switch combinations which still feed back to various control modules. What this means is that everything operates above chassis ground. The various body components, frame, and Eng. ground are still important as some signals use these conections in a mutiplexing fashion. ( which I absolutely detest)