Please add to this thread for ground connections but in my experience with GM vehicle, the grounds should be:
- Cable between battery and engine (alternator bracket, water pump bolt, or bolt on front of block by fuel pump)
- Cable between battery and vehicle body (inner fender usually)
- Cable between engine and vehicle body (firewall and valve cover bolt usually)
- Cable between engine and chassis (valve cover bolt and frame)
- Cable between chassis and vehicle body (under cab)
I had to add one between my cluster and firewall because of the usual cluster lighting issues many have.
A simple check to see if you have a ground problem (slow crank when hot for example):
Take a set of battery cables (which you were going to ask for a jump start for the slow crank issue anyways) and do this:
- Hook one end to the engine block, the other end to the frame.
- For the other jumper cable, connect one end to the body and the other to the frame or engine block.
- If it cranks OK, verify you have good, clean, and sufficient grounds.