Under Tailgate brake light

So I got the Opt7 that @Amateurhour suggested with the 7 to 4 harness. With just the harness on I am getting a fast blink on my turn signals, and when the bar is connected the same with no response on the light bar. I start it again and now it thinks a trailer is connected, I tell it no trailer/accessory in the trailer screen, but it keeps telling me to check trailer lights and switching profiles.

Has anyone else run into any of this?
 

Oh that sucks. I used the harness that tees into the taillights not the 7-4. https://www.opt-7.com/collections/c...t-harness-for-2019-2021-silverado-sierra-1500

It looks like Putco also offers a factory plug and play harness that they list as working for the 2020-25 trucks: https://www.putco.com/product/blade-quick-connect-harness/v/GMC/Sierra 1500/2024/

Sorry, i’ve got no help about the 7to4. Although if you do get it working it might activate your side cameras when the blinker comes one.
 

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Oh that sucks. I used the harness that tees into the taillights not the 7-4. https://www.opt-7.com/collections/c...t-harness-for-2019-2021-silverado-sierra-1500

It looks like Putco also offers a factory plug and play harness that they list as working for the 2020-25 trucks: https://www.putco.com/product/blade-quick-connect-harness/v/Chevy/Silverado 1500/2022/

Sorry, i’ve got no help about the 7to4. Although if you do get it working it might activate your side cameras when the blinker comes one.
The adapter I am using is https://www.opt-7.com/products/opt7...-to-43-inches-4-pin-extension-adapter-harness
I wish I could find one that goes onto the harness to the tail lights but I have not found one that fits the 24 Sierra 1500.
 

I honestly don’t think that they are any different for the refreshed trucks. I don’t have a 24/25 to test but the opt7 harness for the 19-21 looks just like the putco harness for the 19-25s
IMG_0298.webp

IMG_0299.webp


You could always order the putco harness, it uses the same 4-flat plug that the opt7 does.
 

I just butchered the one I bought and hard-wired it in. I had already cut the ground wire to connect to the chassis to see if that was part of it so I couldn't return the harness. Apparently GMC changed the wiring on the taillight connector for 22+ which is why OPT7 says there's doesn't work. I just wanted to be done with this and start figuring out how to get my head under the dash to mess with wiring on the BCM for other things...
 

That’s what I don’t understand, I have a refreshed 22, and it works fine. And putco lists the same harness (pn# 529005) for a 2020 as well as a 2024 🤷 I don’t understand why opt 7 says that it won’t work.

So were you able to make it work? Used some posi-taps?
 

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