Does the disc need to remain in the trunk unit for the nav to work or does it have memory to store the info?

 

The 3G TL Navigation system requires a DVD in the trunk drive unit for the Navi to work.

New discs run about $185+ shipping.

I do not believe you can use a version older than the one last installed in the car (i.e. no 3.50 disc in place of a 3.70 disk, or using an '04 DVD in an '06 TL) either, due to software updates on each updated DVD.

Also, the '04-'06 TLs use an orange "3.XX" DVD and the '07-'08 TLs use a white "4.XX" DVD; the white and orange DVDs are NOT interchangeable.

Welcome to AZ.