# 2020 GMC Denali 3500 hd



## JIM D (Nov 16, 2006)

Morning all--
I have a 2020 GMC Denali 3500 hd SRW Duramax Diesel with a snowplow prep package. Does anybody know where to locate the switch for the roof mounted light beacon?


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## Philbilly2 (Aug 25, 2007)

I believe somewhere I saw or heard it is in the lights setting in your radio?


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## Philbilly2 (Aug 25, 2007)

Philbilly2 said:


> I believe somewhere I saw or heard it is in the lights setting in your radio?


Correction...

Button on the overhead panel.


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## JIM D (Nov 16, 2006)

I've owned GM heavy duty pick-up trucks since 2003, and am very familiar with all of my past vehicles as to the location of the on/off switch for the roof light, but I'll be damned if I can find the one on this truck.....its not there....


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## Philbilly2 (Aug 25, 2007)

from the manual


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## JIM D (Nov 16, 2006)

is that manual for a 2020? My manual shows no such illustration, or instructions, nor does the button exist in my vehicle. Keep in mind, I have a GMC, not a Chevy


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## 1olddogtwo (Aug 6, 2007)

Check glove box, see if it's a customer install item.


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## Mr.Markus (Jan 7, 2010)

I thought it only came with snow plow prep, i couldnt find a denali with SPP. Did you order it or buy off the lot.?


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## Philbilly2 (Aug 25, 2007)

JIM D said:


> is that manual for a 2020? My manual shows no such illustration, or instructions, nor does the button exist in my vehicle. Keep in mind, I have a GMC, not a Chevy


2020...

But you are correct it is a Chevy


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## Philbilly2 (Aug 25, 2007)

Mr.Markus said:


> I thought it only came with snow plow prep, i couldnt find a denali with SPP.


I thought the same...

OP - Do you have a sunroof or a sliding rear window on your Denali?


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## JIM D (Nov 16, 2006)

ordered the truck, ordered it with SPP, and yes, it has both a sunroof, and sliding rear window......I've asked the dealer, and I've attempted to reach out to GMC, but nobody seems to have an answer....unreal....


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## Kevin_NJ (Jul 24, 2003)

If nobody else knows you could try GM Upfitter.
https://www.gmupfitter.com/contacts/contact_us


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## fireside (Mar 1, 2008)

its an option for the roof mounted light switch. so you may not have that option


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## Philbilly2 (Aug 25, 2007)

VYU is the RPO code for the plow prep.

What is the SPP code?

Sunroof and rear slider are not options with VYU code. They cancel when you are entering your order.


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## JIM D (Nov 16, 2006)

I do have the option RPO VYU listed on my build sheet. I did try GM Upfitter, and it looks as though there is a bulletin #157, it says the wiring is in the rear spoiler of the 3'rd brake light assembly. You need to drill a hole in the spoiler assembly (it fails to mention what size bit to use), fish your wires out, waterproof everything with your own gromet, and then there is a provision to mount your own switch somewhere underneath the dash-board.......this is hard to swallow after spending a considerable amount of $$$ for a new vehicle


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## JIM D (Nov 16, 2006)

Philbilly2 said:


> VYU is the RPO code for the plow prep.
> 
> What is the SPP code?
> 
> Sunroof and rear slider are not options with VYU code. They cancel when you are entering your order.


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## Philbilly2 (Aug 25, 2007)

Curious as to how you got VYU withers the slider and the sunroof?


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## JIM D (Nov 16, 2006)

we bought 2 almost identical trucks.....1 has a sunroof, one does not....we cannot find any type od on/off switch in the truck that does not have the sunroof either.


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## JIM D (Nov 16, 2006)

Philbilly2 said:


> Curious as to how you got VYU withers the slider and the sunroof?


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## JIM D (Nov 16, 2006)

I'm curious too, but it was a definite "need" option for me, I was very specific when I ordered it, and as I sit here typing this entry with the build sheet in front of me, its on there clear as day. VYU snow plow prep---increased front GAWR--roof emergency light provisions w/ pass through......guess GM must have cut some costs by not providing a factory switch


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## Philbilly2 (Aug 25, 2007)

JIM D said:


> I'm curious too, but it was a definite "need" option for me, I was very specific when I ordered it, and as I sit here typing this entry with the build sheet in front of me, its on there clear as day. VYU snow plow prep---increased front GAWR--roof emergency light provisions w/ pass through......guess GM must have cut some costs by not providing a factory switch


That is odd.


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## fireside (Mar 1, 2008)

Its like buying Factory up fitter switches from GM. Only to find out I need a harness to use them well GM part number on GM up fitter is not a valid GM part number Go figure. So I bet you need to buy a Factory switch.


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## Philbilly2 (Aug 25, 2007)

I did some more digging today.

Do you have RPO code TRW on your build sheet?

Because according to the GM upfitter website, a 2500HD standard 6'9" box, crew cab (assuming your denali is that configuration) has some of the other snow plow prep items, but the roof mounted provisions are not an option on that model/cab configuration.

https://www.gmupfitter.com/files/media/photo/1278/2020_LD_Snow_Plow_REVISED 6_18_2019.pdf


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## Philbilly2 (Aug 25, 2007)

Philbilly2 said:


> Sunroof and rear slider are not options with VYU code. They cancel when you are entering your order.


And I was wrong about this too now. 

I tried to build a 2020 today and you appears that you can get a sunroof on a 2020 with the plow prep

I swore that when I built my 2019 Denali HD on GM's build site earlier this year, it would kick the snowplow prep out if you selected the sunroof, so I tried to build another today just to see and that part was correct.


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## Philbilly2 (Aug 25, 2007)

Philbilly2 said:


> What is the SPP code?


SPP = Snow Plow Prep 










Sorry bout that one fellas...


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## JIM D (Nov 16, 2006)

Yes, I had a 2015 Denali, and you could not have sunroof with plow prep......this was something new for 2020, which is why I've been running around like a dope trying to find the damn switch. Dealer is very little to no help, and the GM center was not helpful either....you would think somebody would have an answer. Like I said, I took FIRESIDES advice and went on GM up fitters and the bulletin tells you to drill a hold in the rear spoiler


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## Newdude (Dec 4, 2006)

JIM D said:


> I'm curious too, but it was a definite "need" option for me, I was very specific when I ordered it, and as I sit here typing this entry with the build sheet in front of me, its on there clear as day. VYU snow plow prep---increased front GAWR--roof emergency light provisions w/ pass through......guess GM must have cut some costs by not providing a factory switch


To quote the bulletin: https://www.gmupfitter.com/files/media/photo/1329/UI Bulletin_157.pdf



> Inside cab Wiring
> 
> The inside the cab wiring provisions are in a connector located under the Instrument Panel as shown above in figure 3. This connector has its mating connector installed as a protection for the terminals in the IP harness side of the connector. *This mating connector/cap can be used to connect a relay/switch (customer/upfitter provided)* to power the beacon by populating the cavities for the circuits required to activate a relay (suggested) and for switch power/ground. See suggested mechanization below


For the wiring, Double and crew cab trucks will have the spoiler. Regular cabs don't.


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