Download this unlocker, copy contents to the root of your SD card. Power on the AVIC-S1...then select Yes to All when asked.
http://benji46.free.fr/GPS/WinCE%20Unlocker%20V3.rar
download the following Miomap software and copy all the contents to your SD card :
http://www.mininova.org/tor/773165
Copy the maps into the MAPS folder :
maps - http://www.mininova.org/search/?search=miomap+220
Now, use the windows CE explorer to navigate to your storage card and run MNAVDCE
Contents of SD card :
EASY !