Two Ways to Install a Trailer Brake Controller on a 2008 Dodge Ram 1500 with Factory 4-Way Wiring  

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There are 2 ways you can install a brake controller. On a 2008 Dodge Ram with a factory 4-Way, we usually recommend a hardwire installation using a 4 and 7-Way installation kit # ETBC7. It includes an adapter that is just like # C57674 but it also comes with everything else you will need to complete the installation of your P2, # 90885. However, there is an alternate method which I will also explain after the ETBC7 explanation.

The 4-Way on your truck has the lighting functions for a trailer only and does not have the wiring run back for the electric brakes, 12 volt power, or reverse lights. That is why you have to hardwire in the ETBC7. The wiring for a brake controller may also not be present so it has to be hardwired in as well. The ETBC7 provides everything you will need.

If the trailer does not need a 12 volt feed or reverse lights then you will not have to wire those in. You will still need to run a wire from the brake controller blue wire all the way back to the adapter blue wire for output to the trailer brakes. The white wire on the adapter must be grounded to the truck frame.

I have included some links that explain the ETBC7 installation for you.

The second method is a little different. It is possible that your Ram has a factory port in which you can plug in an adapter to go from the controller to the truck. The harness is # 3020-P. I have linked a video showing where it would install (underneath the dash, to the left of the steering column, taped to another harness near the emergency brake pedal).

However since the truck has a 4-Way and not a 7-Way, the factory side may not be fully functional so there are some additional steps to take to complete installation. First consult the owners manual for the fuse location for power to a brake controller to insert the proper sized fuse. If the controller powers on then you know it is connected from the power distribution box to the factory brake controller port. If not, then you will need to hardwire the controller after all.

For the brake output wire, it terminates near the front wheel well in a connector. Usually located under the driver's side of the vehicle, right behind the front wheel well is a wire connector. There are more wires on the hood side (right side) of the connector than the hitch side. Using a circuit tester like # PTW2993 you can locate the wire that supplies power to the trailer brakes. Usually, it is the blue wire.

You will need to tap into this wire using wire # 10-1-1, sold in 1-foot increments, and run it all the way back to the adapter, like # C57674 blue wire. Enough wire will be needed to make it from the front wheel well to the end of the truck bed. After mounting the new trailer adapter and plugging it into the original 4-pole connector, installation is complete. Do not forget to ground the white wire to the frame.

Often times the connector in the wheel well area is difficult to get to and since you need to route wires anyway we normally recommend a complete hardwire installation. I have included some additional links to help with this second method of installation.

expert reply by: Michael H

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