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:
Visual Index
...
Transmission Range Switch Replacement (A/T)
Raise the vehicle on a lift, or apply the parking brake, block the rear
wheels, and raise the front of the vehicle. Make sure it is securely
supported.
Shift to N.
...
Rectifier Test
Check for continuity in each direction, between the B terminal and P terminals,
and between the E terminal and P terminals of each diode pair. All diodes should
have continuity in only one ...