What Wire Colors do I Need to Attach for Installing Roadmaster Smart Diodes in 2024 Sierra 1500?
Updated 08/15/2025 | Published 07/18/2025
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Question:
I have a 2024 GMC Denali 1500 I am towing with a 2020 Tiffin 33AA red 360. I have Airforce one braking system. To get the taillight and brake light to work is all I need is roadmaster 789 smart diode LED for the truck LED light to work. Do you know which wire color on truck to tie in to. thank you
asked by: Joshua C
Expert Reply:
Hello Joshua,
I really wish I could tell you exactly which wires to tap into on your 2024 GMC Denali, but unfortunately, we don’t have access to the vehicle’s wiring schematics, and based on my research, it looks like GM doesn’t publicly document those internal wire colors online.
What you'll need to do is use something like the Hook Probe Circuit Tester # PTW2993 to test each wire for function.
We did a similar install on a 2018 GMC Sierra 1500 using the Roadmaster Universal Hy-Power Diode Wiring Kit # RM-152 (attached for reference). That said, I would still recommend checking for function on your vehicle, as it’s six years newer and wire colors may have changed. According to the Roadmaster Fit Master, you can use # RM-152 instead of the Smart Diodes # RO54FR.
I really wish I could just give you the wire colors, but you’ll need to confirm them with testing.
Apologies for the delay getting back to you, we had a surge in questions and are working on catching up. Are you new to flat towing, or just getting a new vehicle set up?
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Demco Wireless Coachlink Braking Monitor for Flat Tow Brake Systems
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Kate F.
8/15/2025
Hey Joshua, Did you get a chance to test the wires on your 2024 GMC Denali with the circuit tester? I'm curious if you were able to get the taillights and brake lights working with the diode kit. If you need any more help, just let me know!