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Adding floor lighting to a 2024 HD

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Hopefully my go to guy for HD electrical stuff stops by this weekend. I have a set of LED clear lights installed under the dash at the driver and passenger feet. All I need at this point is to make a 12v+ connection to the BCM plug that controls the interior lights. A circuit can be added according to document ID 85527849. Someone else posted that info on here a while back but I cant recall where it was. A special connector is required and the plug needs to be removed from the left dash at the kickpanel to facilitate the install. I am only installing the additional lights in the front since the rear is where the dog rides and 90% of the time the seats are folded up. They could easily be added though. 


Since the 24 has the different architecture I wasnt able to install them like on my 2021 where I pulled power from the grey wire that ran below the glovebox door. 

Hopefully I will have this by next week. 

Edited by 64BAwagon
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SC;   We need to find that document ID 5862954 you mentioned, in hope of tapping into the Dome/Map light circuit, with the least amount of pain.

I MUST say I am Extremely Disappointed with the interior lighting (Lack Of). For a Denali, or even a basic work truck !!!!!

I did find the wire for the front dome/map lights (Grn/Wht), by dropping the pod. Needed a T-10 Torx driver for 2 deep recess front screws, then pulled down carefully, two rear spring clip fasteners.

Problem is, this is digital voltage controlled circuit. Ramp up & down "theater lighting", goes from -0- to +5.6 vdc.

My first thought is the Option (Code: S0M)($472.00) for that silly Door Sill Lighting Package, to tap into that control circuit. Just to order the wire harness portion of that expensive silly option. If that will power the 4 sill plate LED's, it should power my 4 KC Cyclones, that draw .4 amps ea.

My partner in CNC plasma cutting machines, designs circuit boards. He warned that just adding a D.C. relay to that dome/map circuit, to then power the added LED lamps with a strong fuse panel 12v., the on/off of the relay coil, will probably damage that Transistor circuit in the trucks computer, with back-feeding the collapsing  coil voltage spike, when the relay shuts off.

With his advice, trying to build a circuit he suggested with the mini relay, NTE116 Diode, a NPN tranistor, a 1-10 UF "T." Capacitor, and two 200 Ohm resistors. A lot of f'n B.S. for such a simple need.

Don's Life has a nice You Tube video of an aftermarket Univ. Lighting Kit, with Bluetooth etc., and smart phone app. It did not go into, if you could program the GM infotainment Settings tools,  to turn this on and off with the cabin lighting door open & close cycle.

This is what I'm trying to do with this circuit I'm attempting to build. The Pix attached with the KC Cyclone LED pod rock lights, are powered off the fuse box for a test.

A lot of  cooked brain energy I've spent on this, for what GM should have done in the first place. Do GM  Engineers. and Designers ever get in these trucks at night ??

Will have to add more pix in other posts due to file size.


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Last Pic-6.  Could have found a way to put under the rear of front seats, but moving seats, wires would have to follow the power seat harness for safety. Thought this simple fixed mount works just fine. Small 1/4" dia.  insulated wire clamp and #8 screws and Acorn nut for these KC's.


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The Denali Illuminated Door Sill Kit is P/N: 85136964 $350.00. The wire harness  to the dash must be included in the bill of materials (BOM) in this kit.  See if my GMC dealer parts dept. can break this kit down i to components.

This may be the easiest way to add our additional cabin lighting, as a tap in source.

Denali Illuminated Door Sill Kit #85136964.jpg

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More digging....I know the Illuminated Sill Plate option  code: S0M, is in the list for my '24 2500HD Denali, but these kits work up to a '23, with the older wire harnesses & electronics.

So more digging for these kits for the '24's.

One pic of the kit shows the wire harnesses are included, as suspected.

Must have different wire harness plug type for the '24 dash wire harness connections.



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Just finished adding a light on each front floor area. 

If you search document ID 85527849 you will find the sillplate option instructions. These will work to access the lighting circuit that will control the add on lights. I only used 2 LED clear marker style lamps that I got on Amazon. These were the same ones i used on my 2021. 

If you follow the directions you will have to remove the X1 connector and add a molex connector wire to the 1 position. The instructions outline it pretty well. It is a very tight squeeze to get to it since its the forwardmost connector. Make sure and release the connector before trying to remove it. 

A couple of things to note. When removing the sill plate for your access to the ground, pull the plate on the side of the seat upward and remove it. Then pull the sill plate upward and inch or so then pull it backwards to release the kick plate panel. Its all one piece now, it used to be 2 pieces in earlier years. I used one of the ground studs behind the kick panel. The rest of the wiring is up to you as far as type of light and placement. I would not get too carried away with the size and number of lights. I dont have any data on how much additional power consumption it will take to make the magic smoke appear. LOL

Here is my finished project 


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Here is the sill plate removed and the pic of the ground stud. If you look carefully you can see the blue of the eyelet on the ground stud, there are 2 in this area, either will work.  The red wire with the splice connects to the yellow wire on the Molex connector. I cleaned up the loom and covered the ground wire before putting everything back. 





Edited by 64BAwagon
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This is the yellow wire (I used that color since Yellow is what GM uses for lighting) after the connector is back in place. Not really enough room to get a decent pic but fortunately the instructions are pretty clear. Just be careful that the connector is positively engaged. We were careful to test the circuit with a meter before connecting the lights. If you need to test them you can close the door latch pawl to initiate the lights off and then release the handle and rotate it back to open to turn them back on. 



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I should also add that the instructions for the sill plate mod were posted on here a while back and I got my information from that document. I cant find it again and I dont know what thread it was in but credit to whoever posted it since thats the way I stumbled on this. 

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SC;  Thanks for pix & info.  What part number did you use for the wire harness ?  Or did you have to buy the entire sill plate kit  to get the harness ?

The install document # 5862954 , you first referenced, I found this one # 85527849, shows for a '22 1500 however. Does not list the part numbers in the kit.

2022 GMC 1500 illuminated Sill Plate Install Inst. #85527849.pdf

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Clarification:  The # 85527849 is the entire KIT.  Denali illuminated Sill Plates in Stainless, and wire harness.

Getting used to GM part numbering. I thought it was just the number for the instruction sheet.

The GM accessory web site says this #  Will Fit my '24 2500HD Denali, at $350.00.

The www. GMpartsdirect.com site says this # Will Not Fit my " "            ,at $276.94.


I would think the Molex connectors and pins used are common in GM, but there are different size pins for various current loads. Be interesting to see what wire harness p/n you used. Thanks again. KP.

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