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:
Gauge Control Module Replacement
NOTE: Before replacing the gauge control module,
retrieve the ODO value and the maintenance minder information from
the gauge control module with the HDS.
Remove the instrument panel.
...
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. ...
Removal
Drain the engine coolant.
Remove the air cleaner.
Remove the heater hose clamp bracket mounting bolt (A) and the harness
holder mounting bolt (B).
...