I think I messed this one up bad. Was installing an aftermarket third brake light, cargo lamp combination (LEDS). It did not come with a plug, only bare wires. After figuring out where everyone goes, I was inserting the wires into the main plug and adding tape. Did not disconnect battery, my bad, noticed a small spark (strand of wire loose). Now the radio, interior lights, cargo and park lights do not come on. Also no power door locks. Checked fuses (ok), changed fuses, this is ok. What did I do, besides not disconnecting battteries? Dealer tried to do a quick scan, under dash plug not working. Any quick checks? relays, a fuseable plug, computer parts? Want to leave on holidays in a couple days so any help is appreciated. thanks in advance

 

You don't say what year truck you have, but on 2nd gen, check the IOD fuse. It is in the fuse holder in the end of the dash. I believe it is #12, and has a plastic clip over it.

 

Truck is a '99 3500 dually, 6 speed manual, 5.9 engine. No chips on motor
will recheck fuses looking for this one. thanks

 

2nd that fuse under little black or grey clip on side of dash.

 

That is the one, and likely the cause of the OP's problem......

 

I did find a blown fuse with the clip over it. Changed it, still no park lights,door locks, interior lights or radio. The indicator light for the factory fog light is on at the headlight switch. Does this mean anything? Should I disconnect battery to reset anything? Anything else to look for? thanks

 

Might mean there's a short and the fuse blew as soon as you put it in? Just saying because it's happened to me making me pull my hair out for nothing.

 

Bought new 10 amp fuses, changed them all, still nothing. Checked other fuses, found 50 amp fuse that was suspicious, changed out, all works now.Thanks for all the suggestions and help on this everyone