What is this black box on the firewall to the right of the Master cylinder just above the wheel well?

Good afternoon.

It looks like a junction box of some sort. Can you post a couple more pictures closer and possibly open up the box? It looks like the ne nut may be the cover bolt.

Roy

Thanks, much better.

That is the junction block that connects all the under-hood wiring to the interior. You need to remove the one bolt in the center. That will release the connector. It will pull out.

What happens is there may be bad connections that have caused high resistance and heat is the result and wires gt damaged. Remove the bulk head connector and inspect all the wire inside and the part from inside as well.

Roy

Yep, you have a real mess there. It looks like the junction block needs to be replaced.

You can go to a GM dealership parts and see if they still list the junction block parts. Ask them to check new old stock as well. That will check all over the country.

If not, then you will need to find a used one at a junk yard and change it.

That looks so bad that you cannot even replace just the pins. You need the connector.

Roy

You are welcome.

Feel free to return for any follow up questions.

Roy