P2 Trailer Brake Controller Only Works with Manual Override and Not the Brake Pedal

Question:

When I am hooked up to my trailer, I see the .C. so I know Im connected. I can use the manual lever to get the display to 6 and when moving and applying the manual lever the brakes on the trailer are applied and work. The problem is that when I just apply the brake when moving or otherwise, I get no numbers, just the .C. Im assuming the brakes are not working. Any ideas on why? The controller head is level. Everything was working until about 2 months ago.....

asked by: Kim C

Expert Reply:

This is a problem on the red wire. The red wire tells the brake controller you are stepping on the brake pedal. If that connection has come loose that could be the problem. If the connection is good, then you will want to check for a blown stop light or CHMSL fuse. Use the truck owner's manual to find the fuse locations.

If it is still not working, then make sure the red wire is getting power when you step on the brake pedal. Use a circuit tester such as # PTW2993 to test the red wire while pressing the brake. If no power is on the wire, then make sure the connection is good. If the connection is good and it still doesn't have power, it could be a faulty brake switch.

If the red wire does have power but the controller still does not send power back to the trailer brakes then you will need to check the setting of the brake controller, make sure that the output is set high enough.

And if it still does not work then there is likely a problem inside the controller and it will need to be replaced.

expert reply by: Michael H