Whats the special menu on the nav?
 

A few days ago i read that if you hold select for 5 seconds it opens up some service menu or something, yesterday i watched a video where termx5 did the same. ive tried all buttons and nothing...?

Hold down the select button on the end of the left stalk by your steering wheel. The menu will then come up on the nav screen.

Thats for the memorization of different obc readouts such as time and stuff... Theres another one though

I wasn't aware of another menu.

What functions does it operate?

Ohhhh thanks i needed to go into the settings menu first i guess

Strangely...there's multiple instructions for accessing the service menu...it depends on which set-up you have and which NAV model number you have...try some of the ones below:

In my case i was able to acces the GPS service mode by holding the "menu" button

I will try the "select" mode again as in qsilvers second photo

I couldn't agree more. Makes perfect sense to me.