How-To: GMT900 Cargo Light Mod.

[elcompalaline]

After a fellow member (brims) posted up the necessary info on the wiring for the cargo lights(here is the link, post #11), I went ahead and traced the wiring and installed a rocker switch allowing me to turn them on without the interior/domes. A feature that was so useful in my 04 but not present on NNBS GMT 900s, perfect for those of us with stuff in the bed that could be checked on from the interior of the truck. Here is my "How To".

 

Note: For anyone doing this mod, please be very careful and place close attention to what you are doing. You will be working near the BCM and junction box if anything would go wrong, I will not be held responsible and this mod should be done at your own risk. With a little patience anyone can tackle this just watch what you are doing.

 

Tools needed

-wire stripper/crimper

-flashlight

-electrical tape

-electrical tester tool

 

Materials needed

-(1) rocker switch ($7.49)

-butt connectors ($2.99)

-female wire connectors ($2.99)

-(1) Add-a-circuit ($9.99)

-18 gauge wire (not sure on the price, I had some around from another project)

 

Find your BCM (located under the steering wheel area). On the BCM, the pink connector runs the cargo lights wire (tan wire w/brown line) to the junction box (located a bit lower than the BCM and closer to the fire wall) into a brown connector. This is the wire we need to cut right before the junction box.

 

Once the wire is found, it was time to find a power source. I used the Add-a-circuit and plugged it into the Aux Pwr slot located in the fuse area in the trucks interior (between driver door and dash). The Add-a-circuit has two slots for your fuses, I used (2) 20A fuses to prevent a short.

 

Find a place to mount your switch, I used a little cubby hole under the HVAC controls between the two cigarette lighter plugs. You can mount it any where else that may be easier for you, I just like that when off it is not in plain view. But when on, I can easily see it and remember to turn it off so I don't accidentally drain the battery. Then run your wires behind the dash near the fire wall.

 

You will need (3) wires from the switch.

1.power (this will connect to the Add-a-circuit in the fuse area)

2.ground (I used a self tapping screw and grounded on a dash support just to the right of the gas pedal)

3.accessory (this will be connected to the tan w/ brown wire that controls the cargo lights. It is very important that when you connect this wire, the connection be made to the part of the wire running towards the junction box and not the BCM!)

 

Make all of your connections, try out the switch to make sure it works properly and then put everything back together.

 

Here is the finished product, you can clearly see that the cargo lights are on. Also my interior/domes are not on and of course the rocker switch is also on (it has a nice bright red led). I also made sure I retained the OEM features of my interior lighting by opening closing the door and using the dash switch to manually turn them on. Everything works like a charm and I now have the ability to turn on the cargo lights without the interiors when I want to. Enjoy!

[RayGMC]

Nice...can you post a close up of your switch location?

[elcompalaline]

Nice...can you post a close up of your switch location?

 

Here ya go.

[lsuguy]

Nice post man. This should help out alot of people

[MS3DALE]

Nice write-up and modification on something GM should've done in the first place.

[elcompalaline]

Nice write-up and modification on something GM should've done in the first place.

 

Couldn't agree with you more. Can't remember how many times I have needed to turn them on from the interior, but pointless because you can't see with your domes on as well.

[sillyazz]

Nice write up !!! Thanks for being the guinea pig . Going to have to do this when I get a chance. Thanks Again !!!

[brims]

Nice writeup, glad the information helped.

[elcompalaline]

Nice write up !!! Thanks for being the guinea pig . Going to have to do this when I get a chance. Thanks Again !!!

 

 

Nice writeup, glad the information helped.

 

Thanks guys!

 

Hey brims, with all those wires under there it would have been a major PITA without the info you posted, thanks again.

[brims]

I've done a couple of things with the wiring, you're really screwed without the FSM.

[pj5454302]

Its weird becuse the gmt 800's have a button for the cargo light.

[Visegrip117]

Nice job man,

Looks like a project for next weekend

[grose67]

I have been wanting to this to my truck for some time. I have a switch already on the dash. I just need to run through the manual to verify the wires.

[mfennema]

Anyone know the part number for the switches that actually go in the slot where elcompaLalo put his switch? In my truck I have switches there for traction control, heated windshield washer fluid, etc. I would like to keep the same look and put the same type of switch in there with this mod. Thanks.

[trucc_boi]

dude you copied me! i have my subwoofer amp switch in the same spot!!

 

awesome write up by the way, dont think i will use it though.