I can't get the auxiliary setting of my MOSFET 50x4 Pioneer car stereo.

SOURCE: Can't get auxiliary to work on Pioneer Mosfet Head unit 50x4

you have to turn the AUX input on through the function menu which can be accessed by following these steps

1. with the unit on. press and hold the source button unitl the unit turns of (or goes into demo mode, which is fine)

2. depending on the model that you have, you will have to press and hold the
(volume button or the audio button), until a menu is displayed.

3 . toggle through until you find AUX 1 and AUX 2. i would turn them both on and see which one you have plugged into, then you can go back and turn the other off.

4. once you have change it to ON. press the source button to turn on. the aux option should now be in your source options.

5. also, while on AUX, you can go into the audio settings and turn up the SLA (sound level adjustment) to +4

hope this helps

SOURCE: Need a wiring diagram for

Here is an installation - wiring diagram from the official manual:

In case you'd like a better quality image you can download the full official installation manual from this link. You can also get the official user manual from this link.

In case of a problem or clarification or further details needed, don't hesitate to post me a reply before rejecting my answer.
If you are satisfied, accept my solution.

Thanks and regards
Stelios
direct FixYa link: http://www.fixya.com/users/technical114