FlBowhunter

gmupfitter website https://www.gmupfitter.com/files/media/photo/474/2014%20BBM%20Electrical%20section_10_18_2013_WIP.pdf

Sorry no pics but the diagram in the attachment should show you how to hook it up and where you put the switch and how you get the wires to the bcm really is your choice. I mounted the switch in the plastic plug because I was able to pop it out and mount the switch and wire it on my work bench. Like I said in my post I prefabbed the entire wire harness in a wire loom and tied it off to an existing harness running up the frame rail on the drivers side. once inside the cab popped out the bcm plug tapped the 2 wires. Done

I already tried that found the door unlock signal wire and taped the light signal wire. Used a diode so the signal did not flow both ways otherwise when you hit the cargo light switch the doors would unlock, no luck. I think you can do it with a small relay. I may try this when I have some time down the road.

I don't think that would work. If that was the case you could hold down the cargo lamp switch in the multi-function switch and the light would stay on all the time. You might be able to rewire the cargo light from accessory power with a On-Off switch using 2 relays that could trigger using the factory switch. http://www.emil.matei.ro/onof2.php Not sure it is worth that much effort, might be easier to just add a light with a separate switch.

Hi Guys, 1st time poster, been lurking around for awhile but never had anything useful to contribute. Not sure how useful this is or if it may have already been done but if not here goes. Well I really hated the way you have to go in the cab to turn on your cargo light in the back and after a little research I was able to come up with a really simple inexpensive way to add a switch for the cargo light in your truck bed. Cargo Light Switch.pdf When I took my multi function switch apart I realized it was only a momentary switch that sends a ground signal to the BCM to turn the lights on and off. I then was able to find the correct wires to tap thanks to the gmuppfitter site. I prefabbed the switch with about a 15' wiring harness (26 gauge wire was all I used) and encased it in a small 1/4" wire loon. Then I popped out the plastic plug near the back f the bed on the drivers side and mounted switch in the plastic plug. I then pulled the wire thru the hole and popped the plastic plug back in place. Then I removed the left rear taillight and was able to reach over and grab the harness pull it back to the light and to tie it off to the existing wire harness. I did this all the way to the front of the truck. I came in to the cab thru the large grommet by the parking brake. ran it over to the BCM. Trimmed my wires and tapped the signal and ground wire for the cargo lights. Now I have a switch in the Pickup bed for less than $20 and a couple of hours of my Saturday. The switch actually works like a 3 way as I can now turn it on in the back and then off in the front or vice versa. Because I am just sending the BCM a signal from another source the light retains all the original functions like the battery saver and it turns off when you put it in forward. I have a cover on my truck bed so I just used a Radio Shack switch but if you do not have a cover or cap you may want to use a Marine grade switch. Cargo Light Switch.pdf Cargo Light Switch.pdf Cargo Light Switch.pdf