Depending on the length of time the power was interrupted, your system may require GPS initialization.

If initialization is not necessary, the system proceeds directly to the Startup Confirmation screen.
If the system fails to locate a sufficient number of satellites to locate your position within 10 minutes, the following screen is displayed.

If you are experiencing GPS reception problems:
On-Screen Commands
The system accepts these commands on
any screen. There are over 100 on-screen
commands. Say what is written on the
screen to activate that selection. For lists,
you can say the list item number to ...
Towing Your Vehicle Behind a Motorhome
Your vehicle can be towed behind a motorhome at legal highway speeds up to 65
mph (100 km/h). Do not exceed 65 mph (100 km/h).
Otherwise, severe transmission damage will occur.
When purchasing a t ...
System Initialization
The navigation system must be initialized if
power to the navigation system is
interrupted for any reason (e.g., the
battery was disconnected). ...