hi.
- Connect the service key to the truck.
- Press switch I while turning the key.
switched on.
- Advance to parameter 25 using II.
- Press switch I; the display blinks.
- To check the old value, press only switch I
one more time.
- To modify the value, press switches II / III. Adjust the
new value by pressing switch I.
- After setting the new value, the display stops flashing.

It is the procedure according to the manual, it is a maintenance code, just change the parameter