Others have had the same problem with the Trip Computer option.
When I retro fitted Hi Line sat nav there was no Trip Computer, however it was activated by a session on a T4 unit.
http://www.the75andztclub.co.uk/foru...3&postcount=14
How to enter the service menu.
http://www.the75andztclub.co.uk/foru...80&postcount=3
Dave T