Recommended Flat Tow Wiring for a 2025 GMC Sierra 1500
Updated 09/29/2025 | Published 05/07/2025
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Question:
i need to tow my 2025 gmc behind my motor coach do you have a wiring harness for it
asked by: Howard W
Expert Reply:
We sure do Howard! To control your 2025 GMC Sierra 1500's lights you'll need the Roadmaster 4-Diode Universal Wiring Kit for Towed Vehicles item # RM-15267. This kit includes all the wiring, diodes, umbilical cable, and connectors needed to set your truck up to be flat towed behind a motorhome.
Here are the rest of the parts you'll need to flat tow your 2025 GMC Sierra 1500, including some additional wiring requirements:
Tow Bar and Safety Chains - etrailer XHD Non-Binding Tow Bar item # e84ZR
Base Plate Kit - Roadmaster Direct-Connect Base Plate Kit - Removable Arms item # RM-523198-5
Please note that this base plate kit will not work with the AT4X models with AEV bumper
Battery Disconnect - Roadmaster Battery Disconnect with Switch item # RM-766 for gas item # RM93MR for diesel
Supplemental Braking System - SMI Stay-IN-Play DUO Supplemental Braking System item # SM99251 or item # SM99243 if your motorhome has air brakes and the Roadmaster Stop Light Switch Kit item # RM-751495
High Low Adapter - The tow bar needs to be within 3" of level. If you measure the height of the inside top of the hitch receiver tube on your RV, and the height difference is more than 3 inches above/below the base plate tab height, you'll need a high/low adapter. I have linked a FAQ article that explains all this in more detail along with our selection of adapters.
Product Page this Question was Asked From
Roadmaster 4-Diode Universal Wiring Kit for Towed Vehicles - 7-Way to 6-Way Coiled Adapter Cord
- Flat Tow Wiring Harness
- Splices into Vehicle Wiring
- Diode Kit
- Universal Fit
- 7 Blade to 6 Round
- Roadmaster
more information >
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on Flat Tow Wiring Harness
Jerred H.
9/29/2025
Hey Howard, did you get a chance to set up your 2025 GMC Sierra 1500 for flat towing with the Roadmaster wiring kit and other parts? I'm curious to know how it worked out for you, as it could help others looking to tow their trucks behind a motorhome.