Quote Originally Posted by fpz View Post
I tried this with a Nuvi 755T and it does not work!
On any of the 7xx series here's what you do.

1. boot it up and hold your finger on the battery icon for 5-10 secs and it will flip to the maint mode screens
2. on the lower right corner of the screen hit the NEXT button and you'll cycle to the "Data Card Test Page"
3. your SD card serial number will be spelled out clearly indicated on the upper left of the screen

If you have booted in the car or a home charger (external power) the battery Icon will not appear. No problem, to get to the maint screens....
1. go to the "where to" screen
2. hold the screen just to the left of the clock (where the battery icon would normally be) for 5-10 sec and it will flip to the maint mode screens. If you're sloppy about where you press, you'll flip to either the to the Map or Clock screens, depending on where you fat fingered it.

It all works fine... I do it all the time on a 755T and others.

Quote Originally Posted by Burn666 View Post
It's not the (Checksum) number you need it's the 10 digit code. Second picture where it say serial 2691044652 that’s the number you need, obviously your SD card Serial number will be different

Also in some models you need to hold down the battery icon not the clock

Hope that helps
FYI - not a SD cards have a 10 digit serial number. I've used a few with less digits (as seen by the Nuvi). I've never seen more than 10 digits.

I think the number of digits depends on the manufacturer. Less numbers i more frequent in Micro-SD cards.

Quote Originally Posted by EIcojo View Post
Weird, I only got a 6 digit code under serial, on a Nuvi 310
FYI - Not weird at all

6 digits is OK if that's what the Nuvi data card screen says. Some cards have a shorter number. Some folks assume it 10 digits because
most of SD serial are actually 10 digits and the expectation is that it's 10 digits because every Nuvi (I've ever seen) has a 10 digit SN (unit ID).

Quote Originally Posted by dolan19 View Post
Does anyone know how to obtain SD Card Id with a Garmin GPSMap 521 (no touch screen)?
This may sound silly but a "sure" way to find it is put it in someone else Nuvi and check it.

I've never seen a reliable alternative method.