I was scanning electrical issues... I great background in generic troubleshooting, a lot of Automotive experiences.
I don't know too much about Isuzu as I just got my 1999 Rodeo and I'm learning. I thought I help you ALL. I seems the place to check ( max current to ground) would be firewall gromments where the loads and switch control pass back and forth. The small wire (c. .m) won't take much abuse. Frayed insulation to Chassis ground causes most of these issues.
I'm Billdarr i(Old Man from PA & CA) now in Central AZ.... I hope I've helped someone.