Troubleshooting Prodigy P2 Brake Controller 90885 That Shows Trailer Connected When Not Connected

Question:

With trailer disconnected the .c. Light stays on after Ignition turned off.?

asked by: Byron H

Expert Reply:

On the Prodigy P2 Brake Controller # 90885 the displayed message .C. indicates that the unit has 12V power, has its boost feature engaged and that it detects a connected trailer. Since this message appears without your trailer connected the likely cause is corrosion or foreign material trapped in the trailer socket.

What can happen is that contaminants like dirt or water can cause two separate circuits to be bridged together. This could allow voltage from one circuit to bleed over to the brake circuit, fooling the controller into thinking the trailer is connected. You can inspect your vehicle's trailer wiring to see if you can find any such issues in the socket or in the plug that connect to the back of the socket. Corrosion can occur inside a connector as well so check everything and clean or replace connectors as needed.

There is also the possibility that the controller itself has an internal fault. If you have another truck into which you can install this brake controller this will allow you to test it with your trailer. If the problem goes away then you know the problem is on the vehicle side. If it remains then the controller itself is likely to be damaged.

expert reply by: Adam R