Other than taking it to a service center with specialized test equipment? If you can find a similar unit with the same GPS receiver, a non-scientific but effective way is to use the units together and compare results. I have a 1300 and a friend has a 1350 with identical hardware. We compared TTFF (Time To First Fix) and satellite signal strengths with the units and they were identical, both stationary and traveling. To access the satellite screen, press and hold the bars in the top RH corner. Pressing and holding Elevation with take you to a hidden screen where you can time the first fix and check which satellites the unit has locked on to (an x under Eph. represents an effective lock) and at least 4 are needed for the TTFF countdown to stop. I've never used my nuvi anywhere but AU & NA, and have had similar results in both countries in city and regional areas, rarely losing sats even in amongst high buildings with overcast conditions. I doubt it would be much different elsewhere.