I am wiring up the Pioneer DEH-P5550MP headset using an aftermarket wiring harness to join the two.
The only wire that doesn't wire up to the harness that I am not sure if I need to wire up or just ignore is an orange wire with white stripe. It is the "Illumination" or "Dimmer" wire. Anyone wired one of these headsets up and know if I ignore this wire or not?

Yes you can just ignore it, and that means you cannot dim your new Pioneer HU display. In TF Magna the factory stereo does not have dimmer function either.

Does that mean u can adjust the intensity of the lights or you mean it dims down when u switch on the lights and the interior lighting for the console lights up?

My Sony HU dims down when I switch on the lights...

personally i wouldnt worry about it.
i have the same h/u, and it doesnt dim very much when the lights come on, so i would just bypass it

dont u have a switch to dim ya console lights ??
so maybe it hooks into that

I know at least the TJs use the console dimmer knob to control the brightness of the factory head unit.. and in appropriate vehicles, the climate control as well.

When I got my new JVC hooked they seem to only have wired the dimmer switch to the headlights so when I turn the headlights on the display inverts (becomes white on black instead of black on white) which is just fine by me since I left the console at the dimmest setting all the time anyway.

on this head unit it is a case of when you turn your headlights on it dims a little - but cannot be adjusted by the dummer switch (if you look the dimmer switch has 2 power wires - where as this has only one.

but - as they mentioned above - it is not necessary!!

Manual

Thanks guys. I just ignored it and everything hooked up sweet. Only thing is now my car stalls all the time. see post in tech torque for details