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:
Fuel Economy
Improving Fuel Economy
Fuel economy depends on several conditions, including driving conditions,
your
driving habits, the condition of your vehicle, and loading. Depending on these
and
other co ...
Navigation—Changing Route or Destination
You can alter your route by adding waypoints to visit, adding streets to
avoid, or changing your destination during route guidance. ...
Charging the Battery
Disconnect both battery cables to prevent damaging your vehicle’s electrical
system.
Always disconnect the negative (–) cable first, and reconnect it last. ...