Why Would Reverse Light Circuit Flash for a Second When Hooked up to Trailer

Updated 06/29/2026 | Published 06/25/2026

Question:

I have a 2024 gmc sierra denali. When I hook up to my boat trailer and put it in reverse my back up lights will flash and then go off. My brake bypass solenoid also doesnt work. I saw online that gm doesnt send constant 12v thru the system. Is there anything you guys sell that could help remedy this situation? Any hep would be greatly appreciated!! Thank you,

asked by: Steven P

Expert Reply:

Hey Steven, if you touch the reverse light circuit wire on your 7-way when this happens does it got hot or warm to the touch? The fact that it lights up for a second and turns off sounds more like it's shorting out but hasn't popped the fuse than the circuit not being active. Because if it wasn't active it shouldn't flash for second. If the wire gets warm or hot you will be looking for a short to ground on the trailer wiring and fixing as necessary.

expert reply by: Jameson C