Jump to content

2021 Sierra -wiring LED backup lights...electrical experts needed!

seamus2154
 Share

Recommended Posts

seamus2154 Enthusiast

seamus2154

Posted
Posted (edited)

Hey Guys! I have a New 2021 Sierra Denali 3.0 Duramax. Love it so far and have been sorting it out nicely. I have had 3 of the previous generation truck. I always mount LED rear backup lights on the rear bumper as some of the places I race have no lights in the parking lots. In the past I pull 12V power and the reverse light as a trigger wire for the relay for the lights, off the trailer wire connector. Well.......this 2021 does not light up that plug unless the trailer is connected. Once you plug in the truck recognizes a trailer is hooked up. For some reason there is 12V that is on but none of the other wires are live till a trailer is hooked up. I thought something was wrong so  hooked up the trailer and boom everything then works and the display states trailer hooked up.  So...I can get the 12v for the relay but now I am trying to find which wire on the rear tailight harness is the reverse lights? Appears to be the light green one I think?? But this truck is all LED and its a very light gauge wire. Does this truck have a LCM like the german cars.? Light control module. Will it sense a larger load and screw up something?? Pretty common with german cars. Also afraid to mess up any modules? I have wired 10 different pickups this way but the new generation is definetly different! Any advice for a trigger wire on relay?? Is that much of a load to the relay??

 

Thanks

Edited by seamus2154
  • Like 1
  • Replies 31
  • Created
  • Last Reply

Top Posters In This Topic

Popular Days

Top Posters In This Topic

Popular Days

Popular Posts

seamus2154
seamus2154

Hey Guys! I have a New 2021 Sierra Denali 3.0 Duramax. Love it so far and have been sorting it out nicely. I have had 3 of the previous generation truck. I always mount LED rear backup lights on the r

Enough
Enough

I went another route since I didn't want to take a chance cutting and splicing wires.  I bought Curt Industries T-connector 56584 and flat wire extension 58531. The T-connector t's into the big bumper

Transient
Transient

There are some electrical plugs up by the spare tire that allow for the Putco blade tailgate led lightbar to work.  I have that accessory and did the install.  It was plug and play.  The lightbar does

Posted Images

seamus2154 Enthusiast

seamus2154

Posted
  • Author
Posted

No one knows if this truck has a module running the trailer plug or rear taillights ?? Nervous to just use that light green reverse tailight wire as a trigger for the relay and destroy a module. 

This is the stuff I hate about my German cars, cant mod a thing without a computer problem. 

jashaw Enthusiast

jashaw

Posted
Posted

I have a tailgate LED light bar, and light strips that use power directly from the reverse lights. I will have to see what wires I used since it's been a while.

 

Not sure if they're the same as my 2020 RST though.

Enough Enthusiast

Enough

Posted
Posted

I went another route since I didn't want to take a chance cutting and splicing wires.  I bought Curt Industries T-connector 56584 and flat wire extension 58531. The T-connector t's into the big bumper wiring harness behind the bumper and the extension plugs into the T-connector. I then connected my aftermarket reverse lights to the extension. This way nothing in the truck's original wiring is altered.

 

This setup also gives me the option to connect other running lights or turn signals using the remaining wires on the extension with no worry about the trucks original wiring.

 

https://www.curtmfg.com/catalogsearch/result/?q=+56584+Trailer+Wiring+Harness

 

https://www.curtmfg.com/part/58531

 

I bought some cheap Nilight lights from Walmart in case this idea didn't work so I've got less than $75.00 in this setup. The lights are plenty bright but don't wash out the camera at night.

  • Like 1
seamus2154 Enthusiast

seamus2154

Posted
  • Author
Posted

Thats a great option for not cutting the wires, thanks. I dont know if the 2021 Sierra Denali is different that the trailer plug is not active other than a 12V when a trailer is not plugged in. None of the pins light up without a trailer plugged in. Never came across this before. I assume its due to the new trailer package and interaction with the screen?? So if that plug is not live I cant see how the T would work on the 2021???? As soon as the trailer is plugged in, it pops up on screen and prompts for the light test which works perfectly and all trailer lights work. Unplug it and test those pins and nothing but the 12V works. There is a schematic on the plug cover if you look. So i am assuming its going through a module???? 

Thnaks for the input

Transient Senior Enthusiast

Transient

Posted
Posted

There are some electrical plugs up by the spare tire that allow for the Putco blade tailgate led lightbar to work.  I have that accessory and did the install.  It was plug and play.  The lightbar does illuminate white when put in reverse.  Perhaps you could create a harness to work between both ends of the plugs.

  • Like 1
Zelas Enthusiast

Zelas

Posted
Posted
On 7/27/2021 at 10:04 PM, seamus2154 said:

Hey Guys! I have a New 2021 Sierra Denali 3.0 Duramax. Love it so far and have been sorting it out nicely. I have had 3 of the previous generation truck. I always mount LED rear backup lights on the rear bumper as some of the places I race have no lights in the parking lots. In the past I pull 12V power and the reverse light as a trigger wire for the relay for the lights, off the trailer wire connector. Well.......this 2021 does not light up that plug unless the trailer is connected. Once you plug in the truck recognizes a trailer is hooked up. For some reason there is 12V that is on but none of the other wires are live till a trailer is hooked up. I thought something was wrong so  hooked up the trailer and boom everything then works and the display states trailer hooked up.  So...I can get the 12v for the relay but now I am trying to find which wire on the rear tailight harness is the reverse lights? Appears to be the light green one I think?? But this truck is all LED and its a very light gauge wire. Does this truck have a LCM like the german cars.? Light control module. Will it sense a larger load and screw up something?? Pretty common with german cars. Also afraid to mess up any modules? I have wired 10 different pickups this way but the new generation is definetly different! Any advice for a trigger wire on relay?? Is that much of a load to the relay??

 

Thanks

This Is what you want to use. Its plug and play with reverse out.

https://www.putco.com/529005

 

  • Like 1
seamus2154 Enthusiast

seamus2154

Posted
  • Author
Posted
2 hours ago, Zelas said:

This Is what you want to use. Its plug and play with reverse out.

https://www.putco.com/529005

 

Wow, this looks perfect! I put in 2021 and it states it does not fit a 2021 Sierra 1500!!! I am going to call them

 

Thanks for your help, hoping website just isnt updated to 2021? 

kodiakdenali Enthusiast

kodiakdenali

Posted
Posted

I actually just finished a project to add several different lighting systems to the back of my truck. for mine I used a curt adapter for the 7 pin trailer harness and a putco harness intended for tail light bars. I cut up both harnesses and customized them for my exact application, using the curt harness to get 12V and ground and used the putco harness to trigger relays. the backup lights signal to the rear tail light activates a relay which connect power from the 7 pin harness to a set of LED light pods which I have integrated into the corner step pockets. This approach worked very well.

  • Like 1
seamus2154 Enthusiast

seamus2154

Posted
  • Author
Posted

UPDATE:

 

As per Putco the 2021 is different as far as the trailer plug lighting up without a trailer plugged in. The 2021 needs to see the constant draw from the trailer. 

The good news is this blade harness WILL work as needed!!!! Thanks Transient !Thanks Zelas !   BIG Help!!!!

  • Like 1
Stove09 New Member

Stove09

Posted
Posted

I am having this same issue right now. I mounted two 7" led bars to the bottom of the bumper and wired them into the trailer harness like I did on my last 2 trucks (green with white strip for reverse power and solid white for neutral) but they wouldn't work. I tried putting the truck in trailer mode and still nothing because the trailer isn't actually connected. 

Does anyone know which wires to tap into on the taillights are the power for the reverse? they seem to be pretty easy to tap into from under the truck without removing the lights and I do not want to buy a harness that cost more that the lights. 

Stove09 New Member

Stove09

Posted
Posted

problem solved. I tied the power into the light green wire and neutral into the black wire coming off the harness from one of the rear tail lights. For everyone spending over $50 on a wiring harness, on top of whatever they paid for their lights... I spent $30 on 6" double row LED lights, plus electrical tape and some extra 18 guage wire. no need to break the bank on this project!

  • Like 1
seamus2154 Enthusiast

seamus2154

Posted
  • Author
Posted

Happy it worked! I ordered the Putco plug in harness which will get me the trigger for the relay on backup lights. I dont know if it will have a constant 12V but can still tap the trailer plug as that has 12v only. I mounted the lights just awaiting harness. I did use a test light in the taillight harness and it seemed to be the light green wire as you said. My concern was it was very light gauge i assume due to the LED not needing much??

 

The Putco harness was more money than the LED light pods!! LOL 

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Latest Articles

  • Posts

    • diyer2
      Castrol Edge VS Amsoil OE

      By diyer2 · Posted

      I use Amsoil's OE line of motor oil (5W20) in our 19 Hyundai Santa Fe. I noticed today on the web site it now says (47% more wear protection1 than required by the GM dexos1 Gen 2 specification). Maybe I  missed it but I don't think so.
    • StingerZ16
      Looking at ordering a '26 WT because I want a std cab, std bed

      By StingerZ16 · Posted

      The amount of storage in the rear seat area is huge. You can keep all your cycle gear dry and clean back there
    • Sparky176
      Subtle vibration, can of worms opened.

      By Sparky176 · Posted

      Truck in fluid changes and investigate subtle shudder at cruising speeds.  Told them it felt like my ‘14’s shudder when AFM kicked in.   Dealer #1 :  You need a new torque converter.   6 weeks later, after causing other damages to my truck, I get the truck back.  Same shudder exists. New, more violent shifts and vibrations at low speed.  After choice words and a few more weeks of waiting for them to replace my running boards supports, I move on to another Dealer.   Dealer #2:  The cruising speed shudder is DFM.  (I didn’t realize truck had it.) The TCM/ECM needs updates.  Updates will solve all vibration issues.   They perform updates, truck seemed ok in lot.  Not a mile down the road, SERVICE BRAKE PAD MONITOR. Dealer #1 stated brakes were at 4mm.   took truck back to Dealer #2, rear brakes at 2mm and less than 1mm.     New pads/rotors on rear, new pads up front.   truck seems good. Toggle through menus, brake monitor system is disabled.  Huh?  Why? Turn that sucker on : SERVICE BRAKE SYSTEM!     will not reset manually, automatically, or even after pulling negative bat cable for 30min.     Could the TCM/ECM updates the culprit?    A torque converter diagnosis for a “normal” shudder and now I’m thousands in the hole and the truck still isn’t right!  Beyond pissed.  
    • riddler
      Oil Consumption

      By riddler · Posted

      Your right on. 👍🏻
    • c4racer2
      Trim level custom/pro

      By c4racer2 · Posted

      Seats matter a lot.  I would start there - good advise here.  I had a 2018 LT Colorado before my 2026 LT Silverado, and the seats are so much better in the new one it's not even a contest.  That was one thing I always hated about the Colorado and I owned two of them spanning 10 years - but I did it so I could park in the garage mainly.  Now I have a much larger property and a huge barn so I have plenty of parking options and a full size is more useful for maintaining the property and current hobbies as well.  I wasn't evenb thinking about the seats as part of the reason for the move to the Silverado, but after two back to back 700mile road trips I am sold on the LT seats w/ leather 100%.  The other LT features are also nice - one thing I really like is the power rear window on the back window by the bed.  And the lighting in the bed is also very nice to have - I doubt that comes on the lower models.  Power tailgate - also quite useful - it's a heavy slug!  What else - I could take or leave the screen - but heated seats and steering wheel and cruise control on the steering wheel is very useable - I would never want to live without that.  Even the colorados had that.

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...