Tekonsha Prodigy or P3 Used on 2008 Dodge Ram Do Not Operate With Brake Pedal Applied

Question:

I have a P3 and a Prodigy with two separate plug and play harnesses and all have the same problem. Maybe you can help me figure out what is going on. I have had the P3 working for many years and now all of the sudden they both dont work. Controllers will not apply full voltage to the trailer when you push the trucks brake pedal. They will however apply full power to the trailer brakes when you use the manual controller levers. Also, with controllers level to the ground and facing straight foward and you hit the brakes, they show only about 1.2-2 volts while still and while driving. I doubt the problem is the connections, maybe something in the truck/pedal? Its a 2008 Dodge 3500. Thank you,

asked by: Maverick G

Expert Reply:

Any time you have a controller that will work with the manual lever but not the brake pedal, you have a problem on the brake lamp input circuit (red wire) on the controller. This circuit is what tells the controller that the vehicle brakes are being applied. Use a circuit tester like part #PTW2993 on this red wire. You should see power on that circuit while the brake pedal is being pressed.

I am pretty certain that you have a blown CHMSL fuse in your fuse box, which is preventing the input from traveling along that red wire and alerting the brake controllers that the vehicle brakes are being applied. Check the lid of the fuse box, which should have a diagram showing the fuse locations. Check the fuse and replace if necessary.

The chances of both controllers being faulty are slim to none. If you do NOT have a blown fuse, get back with me and we will check some other possibilities.

expert reply by: Mike L