Trailer Brakes Are Not Engaging with P-2 Brake Controller Installed on a 2003 Dodge Ram

Question:

I have a 2003 Dodge Ram with a factory installed 4-pin wiring harness. I had a prodigy brake control installed and the trailer lights all work but the brakes dont. The installer just pluged the 4-pin connector from the controller to the to plug under the dash. What else has to be done??

asked by: jerry f

Expert Reply:

If your 2003 Dodge Ram did not come with a factory 7-Way plug, then you will need to use a 4 to 7-Way adapter, part # 37185. The standard 4-Way plug in the rear of your truck cannot power an electric brake function.

You would install the adapter by plugging it into your existing 4-Way, and connecting the additional wires as follows.

White - Ground, connected to a clean metal point on the vehicle frame.
Blue - Electric brakes, connected to the electric brake wire from a brake controller in the cab of the vehicle. Your brake wire will already be run from the front of the truck, but it will stop at the connector underneath your driver's side wheel wheel. Tap the blue electric brake wire from the adapter into this factory wire.
Black - 12V power supply, connected to the positive battery terminal with a 40amp circuit breaker, like part # 9510.
Purple - Auxiliary wire, connected to reverse light wire if needed to power trailer reverse lights. This wire can just be tied up if not needed.

I have included links below to some additional information on wiring for a brake controller, as well as a video showing the # 37185 adapter being installed on a similar full-size truck.