The after market harness comes with this 28 pin connector that is split to the 26 pin connector it has another smaller black plug that connects to one of the secondary ports on the aftermarket unit, this is your TX+ and TX- green/black goes to blue green goes to pink. its important that they are connected at each connector, they basically go in one unit and out to the other, they also communicate Reverse to the NAV ecu and Television ecu.