I just installed an electric brake controller on my 2007 Grand Cherokee Overland WK with tow package BUT without factory brake controller plug.
I just bought a very good price used Tekonsha P2 brake controller to be occasionally use for towing my 26' travel trailer.
I am putting the controller in the hole beside the left steering wheel. Put away in glove box when not in use.
-pigtail wire harness originally comes with the brake controller
-5 feet insulated 14 guage 2 wires inside
-auto reset automotive 30amp circuits breaker
-some clips and end to connect wires
-pliers, cutter, screw driver...etc
Cut a hole to fit the harness end
Open the kick panel, swing all the way down to take it off, unscrew the 2 screws on the corner of the black panel under the kick panel right above the brake and gas pedals
Find the green wire which is for the trailer brake, it is hidden on the left very high bundle up with a huge wire harness, you can just put your hand right behind the fuse panel near the firewall and there is a wire loop around there, just pull the loop to find the end. Connect that to the blue wire on the controller harness for trailer brake.
Connect the red wire from the controller harness to the jeep's brake light signal, the plug is right above the brake pedal, not the one in the front, there is another flat plug with 6 wires higher on the right more to the back or behind the pedal arm, the 2nd wire on the right (white with tan)
Feed the 12v power and ground through firewall, there is an extra firewall entrance with a rubber cap right behind the engine on the right side; when look from the inside, it is right above the gas pedal.
White to the white on the controller harness for ground.
Black to the black on the controller harness for 12v power.
Attach the white wire to the battery negative. And remove the whole negative terminal to work on the battery now.
Cut the black somewhere between the firewall and battery to put the circuits breaker then attach to the positive battery.
Double check all wires, and reconnect the negative battery.
Reverse all the steps to install panels back, and feed the plug through the hole on the left pocket.
Plug in the brake controller, hola! Nice install, working great.