Violet & White 3rd brake light wire

[TPBC]

I purchased a brand new 2025 Ram 3500 from the dealer in December 2025. I removed the Leer topper from my 2023 Ram 2500 and installed it on the new truck. The violet & white wire that was on my 2023 ran my Leer 3rd brake light with no issue. I connected the topper to the violet and white wire on the 2025 but nothing happened. I disconnected the wiring and tested the wire with both a test light and a meter. No power at all when the brakes are activated. I checked fuses and no blown fuses. From Internet searches people say that some 2025s just needed the dealer to program the BCM. I took it to two dealers and neither one knew what to do. Both said that there is nothing they can program to activate the violet & white wire. I thought the easy fix would be to connect a logic box to the 4 way flat trailer plug in the bed. It definitely activates the 3rd brake light on the topper but it also makes the truck think that there is a trailer plugged into it and shuts off the rear sensors.
Has anyone else had this issue and found a solution?

 

[HarryS]

Don't you have a 4 position connector for the chmsl?

 

[Wild one]

In case you don't know what Harry is talking about CHMSL = Center High Mounted Stop Light :aka the 3rd brake light.

 

[Marvin E]

I am curious about the 4 position connector location? I have a friend with a 2025 D3500 and we connected his cap brake light to the white purple and no power. we disconnected and checked and no power. thanks for any info.