Hab was gefunden im www :....viel Spaß damit......
Service mode firmware for nuvi310/360T (taiwan)
Let's use the updater, PRE-BOOT mode and some modified self-made service firmware.
You have to rename 065501000210tw_cure.rgn to 065501000210.rgn before use with updater.exe (tool from garmin update site)
Start the device in the pre-boot mode. (hold the POWER button until the LOADER message appears) Pay attention that PRE-BOOT mode string is not displayed by 2xx nuvi, but other version such as 3xx and 6xx display it.
Attach the device usb. (May be delay while PC searched and installed drivers)
Run updater and select nuvi.
Click ok and proceed. Agree with updater if any additional messages appeared.
If LOADER appeared on the screen you may release POWER button and wait until unit flashed.
After success flashing unit restarts. (if you used WebUpdater before - gupdate.gcd needs to be deleted too! because of unit automatic firmware update after boot if this file exists, now it is no need in it, we will made it manually)
Now unit should boot! And there is only basemap shown (no gmapsupp, no gmapprom, gmapprom1 visible).
And now you can attach it as a Mass Storage Device and DELETE wrong gmapsupp (or whatever you need).
Then you need to make flash for usual firmware for unit. I prefer usual firmware loaded in PRE-BOOT mode, I hate gupdate.gcd 
So, user the file
You have to rename 065501000210tw_orig.rgn to 065501000210.rgn before use with updater.exe (tool from garmin update site)
(replace old cure firmware).
and use it as I described above.
Now your nuvi is fully operational and have no "bad maps".
ein paar Links dazu :
http://garmin.com.tw/products/Nuvi360_TWN/download.html#SW
http://e-trex.info/fw/nuvi/310…i310_360_tw_v210_cure.rar
viel Spaß damit......