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:
Installation
Hold the gearbox housing using a C-clamp (A) and wooden blocks (B) to a
workbench as shown. Do not clamp the cylinder part of the gearbox housing in
a vise.
...
Audio Control Display
Press the AUDIO button to display the audio system on the
navigation screen.
...
Radio Commands
Radio*
Radio on
Radio off
Radio select FM1
Radio select FM2
Radio select AM
Radio tune to # FM (#: frequency,
e.g., 95.5)
Radio tune to # AM (#: frequency,
e.g., 1020)
Radio seek up
Radio s ...