2015 hd3500. Have a boat with electric over hydraulic brakes and last time i towed i got trailer brake message and brakes do not work, yesterday lights didn't work. I hooked my small trailer to the 4 pin plug and no lights but when i turn on a turn signal the trailer hazards flash. Looked at trailer fuses in engine bay and all good. Any ideas? Was thinking trailer brake module under the frame in the back but does that control the lights too?