I've installed an aftermarket radio into my 2006 Mazda MPV. Using the following diagram that I got from MAZDA Car Radio Stereo Audio Wiring Diagram Autoradio connector wire installation schematic schema esquema de conexiones stecker konektor connecteur cable shema (tehnomagazin.com):


I connected pin N to the single steering wheel wire from the headunit. I noticed that unless I connected pin P to ground, I wouldn't get any steering wheel programmability. I tried connected pin P to the headunit steering wheel wire (nothing), both N and P to the head unit steering wheel wire (nothing).

So with pin N to the head unit steering wheel wire and pin P to ground, I'm able to program three functions. I notice that some controls on the steering wheel (e.g. volume up and volume down) end up doing the same thing (e.g. I program volume up to increase radio volume and volume down to decrease radio volume, then either button results in either increasing the radio volume or decreasing it, depending on what function I programmed last).

Has anyone been able to get all of their steering wheel controls to perform separate functions? If so, did your aftermarket radio also only have one steering wheel control wire? I'd like to be able to have vol up, vol down, forward, reverse, mute, and mode. Thanks!