Map light mod issues

Hello! This is my first post here. I have been reading up on the map light mod and tried doing it yesterday but am now blowing my map fuse. I have a 2004 3.4L V6 crew cab. What I did was take a quick wire splice from auto zone and spliced into the live wire that comes from my dome light. I then ran a wire to my map light and spliced into that. My thought was that both my dome and map light already have ground so if I just connect them with a live wire when I open the door and the dome light gets power so will the map light. I did this and when I tried it out only one of the map lights turned on when I opened the door. It then blew the fuse. I got another fuse and put it in and it blew that one in about a minute and the lights still weren’t turning on when I opened the door. They would turn on when I manually switched them on. I installed LED in all of the dome and map lights. I was planning on putting one OEM light back in my map lights because I heard the computer is looking for a certain amount of resistance to turn on the lights and this would save me from putting in a resistor. Why do you think I am blowing the fuse? What did I do wrong? Thank you for any help!

 

It's a switched ground system. You should find an EWD and go over that before splicing wires together.

 

Agreed, you can't just start splicing wires in without knowing what your tapping into.

The Body ECU supplies Power to both the Dome Light and Map Lights on the Black wire and switches the Ground to the Dome Light on the Black/White wire to turn it on and off.
You run the risk of smoking the Body ECU by shorting the dome light wire.
I know how to do the mod on a 2nd gen but I'm not sure how or if it's even possible on a 1st gen.