How to fix bad ground from battery in 98 grand prix

The red post is the positive one, not the ground/negative. It could just be a bad connection at the terminal, in which case you can replace the terminal end. They sell those at any auto parts store. If you would rather have a shop do it, should be about a hundred bucks for them to inspect the battery wiring harness and replace both negative and positive terminals and make sure you don't have any other opens or shorts.

I personally don't like those add on ends that most auto parts stores sell as they end up with a lot of corrosion inside and then you have a bad connection. Replacing the whole cable is better if you can afford it.

How can i fix my ground wire on my 05 grand prix my boy friend cut it tryn to replaced the whole cable