Controller stays on all the time. No change when my trucks brakes are released. Unit continues to apply voltage to the trailer brake system. I tried two different cables, including the cable made by Prodigy for my truck. It is a P3 controller... the rest of the information is below.

I think they have a lifetime warranty, at least they used to. Take it back to where you bought it-I think they'll do a swap out over the counter.

It worked fine with the equipment trailer, but when I attached the 5er it started this immediately. No warning messages came up on the Prodigy.

I'm not sure but some controllers do not work with all brakes.Check to see whether the brakes on the 5er are standard electrical ones.

Typical electric brakes on the 5er. I have had it for a year and worked fine with my other cheap controller. I will return the controller.

This was a problem with the factory wiring harness. Made incorrectly fixed now.