I've got a 2005 Tahoe with the non-lux Bosesystem with touchscreen Nav. I just replacesd the head unit, and updated the disc but it still gives me a "no map disc"message and when it does work, it's not for long!
Anyone have any ideas, know if any control modules that could be at fault?

 

You may want to try and clean the Nav disc. You may mention that you replaced the headunit. Was there something repaired with the unit. Also, you note that you updated the disc. If you have the old disc, you should try it and see of the unit can read the old disc. If it does read the old disc, there is something wrong with the new one.

Cleaning Procedure:
How do I Clean a CD or DVD? (with picture)