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:
Map Screen
...
Guidance Menu
MAP MENU (on map)
►Guidance Menu
Display the guidance points and freeway exits for your route, and set the
display
mode for the map and guidance screens.
Select an item.
The following ...
CKP Sensor Replacement
Raise the vehicle on a lift.
NOTE: Make sure the vehicle is level, because engine oil will drip out
when you remove the sensor.
Loosen the bolt (A). Remove the bolt (B) and ...