is it needed,is it good practice or just overkill?,02 grand cherokee

I run a ground wire to all my electrical parts! Probably over kill, but I believe you can't have too many grounds. I'd rather err on the overkill side of things. Its not like its something that is hard or expensive to do. Gene

https://www.amazon.com/Stainless-External-Marine-Bolt-Supply/dp/B071J75LLQ?ref_=fsclp_pl_dp_

I like to use toothed washers like this between the unit and it's mounting surface along with a bit of grease to avoid corrosion They are available at most any hardware store in most any size.

The case of the pcm does not supply the ground to it, but you wont be doing any harm.

I use the same thing but I also cover it, when done, with women's clear polish they put on nails. Odd but it works