Grab a magnet from a drum brake system and wire it in to the signal wire. It will send enough of a signal back to make the controller work. I used a magnet from a 3k pound system. It's quick and easy and it is a sure fire way to at least get your boat home to figure out the brakes.

How does the 08 Chevy (factory) brake controller work. I bought a new 2500 last night and am now thinking about converting my trailer to EOH.

Is there a downside to doing the EOH, like what if my truck is in the shop and I need to use a freinds truck that doesn't have a controller, just tow with no brakes? Another is what if the unit on the trailer fails when you are towing due to water damage (whether towing with your truck or not), once again, no breaks! Are these legit concerns or old school thinking?

Yes, if you use friends truck with no controller or a controller that is not compatible, then no brakes.

Regarding failure, unless you're one of those guys that backs his truck in half way in the salt water and totally submerging the electric pump etc... then there really isn't anything to worry bout. The electric portion of the system is or should be close to end of tongue. From there back, it's all hydraulic and the system won't care. I have gotten salt water on mine before and just rinsed it off. It's pretty tolerant so far. I recomend stainless calipers with the cadmium rotors. Stainless rotors crack very easy under heat where the cadmium don't. I love mine.

Sorry, I don't know anything about your factory controller but I bet it's a nice one.