Thanks to those who replied. I have been looking further into the setup. I have found on the Curt website they do a 4 pin plug in to 7 pin outlet, seems tidy and simple to do, it also has additional wires that I assume take the trailer brake addition. They also do a trailer brake kit and associated wiring harness. Has anyone tried this setup and do you have to run an additional wire back.
If you use the Nissan 7 pin kit and the Nissan harness for brake controller I assume the wires are already in place. However reading the thread on the connection of the P3 to the Nissan harness it was not plug and play - or did I misunderstand the wiring match-up.
It say on Courtesy site you need a relay after 06, is this for 06 or from 06 onwards?
P3 plus harness
http://www.etrailer.com/multi-product.a ... &hunter=bc
Curt also does a duplex plug with both 7 pin and 4 pin that plugs into the existing 4 pin for $29 and some controllers and harness options. Anybody used Curt stuff?