With pioneer tv's you only have to ground the light green parking brake wire, however the new ones need to be reset every time the ignition is reset or switched on and off, so you can use a switch or if a switch is just too much of a hassle for you, then wire a relay using the remote output of the radio to trigger the relay, and reverse polarity to ground and using that switched ground output of the relay for your parking brake input on the radio. (pin 85 and 87 ground / pin 86 blue/white remote / pin 30 light green parking brake)