Custom Trail Boss Fog Light Install

Brendan Burns · May 21, 2020

Has anyone taken a Custom Trail Boss and done the LT Trail Boss fog lights on it? I am looking for a plug and play kit if there is one out on the market. I'm trying not to source every single individual part from GM. I'm pretty sure I would have to go get the BCM reprogrammed if I'm not mistaken.

JeffC · May 27, 2020

Spent the money for the GM fog lights that fit the opening, wanted to run them when high beams were on, or when ever i wanted them. Just wired up a simple switch on dash. Replace the crappy halogen head lights first, than install the fogs.

Edited May 27, 2020 by JeffC

Railroad_Jim · January 26, 2021

On 5/21/2020 at 6:42 PM, Brendan Burns said:

Has anyone taken a Custom Trail Boss and done the LT Trail Boss fog lights on it? I am looking for a plug and play kit if there is one out on the market. I'm trying not to source every single individual part from GM. I'm pretty sure I would have to go get the BCM reprogrammed if I'm not mistaken.

I just added the factory fog light kit to my 2020 Custom Trail Boss and am very happy with them.

I had been thinking about getting them for a while, and got an email from Chevrolet just before Christmas saying that my rewards points (earned when purchasing the truck) could now be used towards accessories. I followed the link and there was even a site wide discount.

I ordered GM part number 84125494 and there was an option to pay $150 to have the dealer install them. I usually do all work myself, but know that I'd have to pay the dealer to reprogram the BCM anyways, I went with it. I was able to use around $100 of my rewards money towards the purchase, so that helped out.

I chose a local dealer (different than the one I purchased the truck from, which was out of state), to have them installed at. The dealer called me when the lights came it, and I set up an appointment. They took my truck, did the free maintenance service I had credit for, took care of the two warranty issues, and installed the fog lights that same day. I had a nice new Silverado RST loaner truck and everything. And most importantly, it would have taken me months to get around to installing them.

I'm really happy with the factory fog lights. I had already swapped my halogen bulbs for LEDs and the LED fog lights match perfectly, and really help light up the road. It's also cool looking how they come on now when you unlock the vehicle with the remote control. They are controlled with a new button on the replacement headlight switch that was part of the kit.

Here's a picture of the new fog lights installed.

Justin Vaughn · January 26, 2021

Baja Designs makes a GM authorized replacement, I'd look at those if you're so inclined.

Railroad_Jim · January 26, 2021

On 1/26/2021 at 2:15 PM, Justin Vaughn said:

Baja Designs makes a GM authorized replacement, I'd look at those if you're so inclined.

From what I can tell, the Baja Designs are just a replacement for the existing fog lights.

Those of us with no fog lights from the factory, would have no harness to plug these into, or switch on the dash to activate them.

https://www.bajadesigns.com/Products/Chevy-Silverado-2019-Fog-Pocket-Mount-Kits.asp

I went with the GM 84125494 kit as it has everything needed to add the fog lights to a truck not originally equipped with them.

I thought about the Gen5 package from here: https://www.gen5diy.com/products/2019-2020-silverado-1500-foglight-kit

But it's just as expensive, and you don't get the factory fog light switch that I wanted. You have to have them come on with the highs, or lows, or via a separate switch that you need to mount somewhere.

I like the smooth integration of the factory setup, and you can get it for around $230 like from these places:

https://www.gmpartsdirect.com/oem-parts/gm-fog-lamp-kit-84125494

https://www.gmpartsxperts.com/oem-parts/gm-fog-lamp-kit-84125494

https://www.gmpartshouse.com/oem-parts/gm-fog-lamp-kit-84125494

Then you need to pay the dealer to either install them, or just reprogram the BCM to make the new switch work.

Edited March 6, 2021 by Railroad_Jim
Typo

Bikerjon · May 28, 2022

I bought the 85149040 Fog Lamp Package w/wiring harness and dash switch $250.00 with discount from the dealer. Then I bought the gen 5 DIY wiring kit 250500. The fogs come on with the low beams and stay on with the high beams (no switch needed). $154.99 - 15% they are now on sale. I installed them myself. I did not have to replace the headlight switch, tap into factory wiring, no dealer reflash on the BCM and i used OEM fog lamps. Aftermarket fog lamps are not the same quality as OEM and can leak and some have a very poor lighting pattern. I do have the OEM headlamp switch and wiring harness if anyone is interested.

GETGONE · May 29, 2022

I bought the factory light package and wired it up myself. I didn't want to pay the dealer $150 to program the damn BCM to turn on the lights. I had a Fleece Auto high six mod which is just a diode to jump circuits the same as Boost Auto sells only in a nicer package. I tapped the parking light wire on the BCM and the trigger wire for the fog lights so now the fogs come on any time I have the parking lights on. It was $22 vs $150. I could make it myself for a couple bucks with diodes I have laying around.

Dejadoo · June 5, 2022

I've decided to install the OEM fog light kit with the OEM switch (Part # 85149040) and have a couple of questions.

For reference I have a 2021 LT 4x4 LM2 with standard bed. It's the Texas Edition and has the Universal Home Remote, Rear Sliding Window, Heated Steering/Seats, and Trailer Brake Controller.

Plugging in the wire under the driver side dash - I pulled the brown plug to take a look and noticed there is already a wire in the designated slot (brown with white stripe). Installing the new wiring I figure I will need to pull this wire and insert the new, but it begs the question of is it possible to use the existing wire?

To go along with the wire I noticed an existing connection at/under the passenger-side headlight (it's just under the amber colored turn signal bulb) where I would be plugging in the new harness that comes with the kit. Is it possible this is the connection used for those trucks that come with fog lights from the factory?

Has anyone witnessed how/where the factory installed lights are connected?

GETGONE · June 5, 2022

It says in the instructions there may be a wire in that location and to remove it and put the wire from the kit there. Unless you already had a wire in the underhood fuse block, you need to replace the one in the BCM connector with the one from the kit. The plug you see doesn't have anything to do with the fog lights. The harness plugs into the headlight wiring harness.

Dejadoo · June 5, 2022

I've run into a snag - the colored boxes under the cover are coming up with the cover.

I've backed out the fours screws as far as they will go, released all the clips around the perimeter, disconnected the positive terminal, but at least the blue box (maybe more) is coming up with the cover and not allowing me access.

Thoughts?

Ideas?

Dejadoo · June 5, 2022

https://www.youtube.com/watch?v=Na4zJpfeaps

Phastek sure makes it look easy.

Fuse box removal right at 6:30.

Edited June 5, 2022 by Dejadoo
Trying to link to a video

Dejadoo · June 5, 2022

FINALLY!

It seems there are four more tabs that connect to each of the lower modules AND the blue module was NOT being held in place (clipped in) the way it was supposed to be.

With that, there are currently wires installed in the spots specified for the kit (as well as the one under the dash noted in my previous post above). So from the factory it appears I am wired for fog lights, just missing the lights and having them connected - back to wondering about the existing plug just under the RH headlight (previous post above). Wouldn't it be nice if all that was needed was to connect the wiring to the lights right there...