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Changing a GPS devices software version

Started by dleblanc2546, April 16, 2019, 11:42:53 AM

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Good afternoon folks.

So after the April 6th debacle I've come across a very strange issue.  I have a few older Garmin Nuvi 750 units that I compile personal data into a gmapsupp.img file to use around where I live.  It worked great until the 6th of this month but now only works on 2 of my 5 units.

Steps I've taken so far, include:

  • I've made sure to flash all the hard drives of the unit I have so they all the have the same software version on them.
  • I've went through my personal data files to make sure all the units have data that's been specifically matched to their serial numbers so they should work as they did before the 6th
  • Double checked the data to make sure all the region id and product codes match so the maps will unlock for each unit

The only thing I've noticed with the units is the ones that work have a GPS SW Version of 2.20m and the ones that don't are 2.90m.

Does anyone have any idea what the GPS SW Version does?  Or how I can change the version to the ones that work to see if that will resolve my issue?

Thanks in advance.


I can't help with your specific question, but the Nuvi 750 was introduced in 2007. Would be surprised if Garmin made much effort to support a 12 year old device.

And I don't quite understand this part

"I compile personal data into a gmapsupp.img file to use around where I live"

What kind of maps are you making?

"I've went through my personal data files to make sure all the units have data that's been specifically matched to their serial numbers"

The only maps that are tied to a specific GPS device are Garmin products such as City Navigator (or possibly some commercial 3rd party maps). The April 6th issue should not be affecting any of this, unless it triggers some other strange Garmin firmware bug.

Have you tried contacting Garmin support? I wouldn't hold out much hope for a solution, but it would be interesting to see what they say.


With the first part I'm referring to data I collect using a GPS recording device then upload and compile for personal use with private roads not on any known mapping software yet.  I collect area's to assist me with hunting and fishing mostly as well as marking geocache locations, hieroglyphs, or anything else I find interesting so I can come back at a later time at my own leisure.  I keep the other units because I borrow them out to friends with the same interests that also assist me with collecting data for sportsman purposes, i.e. fishing or hunting.  So I just make maps that I can use around my local area that have more data as to what I'm doing at the time.

I tried calling Garmin support and was told to buy a newer unit and try making maps for one of those.  That and I can't adjust the GPS SW Version because of some in-house blah blah blah, I kind of glazed over after they started telling me they couldn't help me and not offering any other suggestions short of buy another device from a different service line.  My only problem is I really don't want to reinvent the wheel because I tried this before and the two units I bought are junk because they will not accept the map data I've created.


OK, I see. But still don't understand the part about different data for devices with different serial numbers. Is that just because you customize the data depending on who you give the unit to? I don't see how GPS firmware version would have any effect on that.

If you just want to try different firmware, it is all archived on this website. IIRC, with an old device like yours, you would change the name of the downloaded firmware file to GUPDATE.GCD and place it in the \Garmin folder on the GPS. When you restart the device, it should ask if you want to install older firmware if a newer version is already installed.

Not sure how this would help you though. Or do you want to install firmware from a completely different device on your Nuvi? Garmin certainly doesn't want you to do that and I don't think it is easy. People used to discuss this kind of thing in the GPSPassion Nuvi forum. But those days are long gone, there is very little interest in the whole field of dedicated automotive GPS anymore, let alone advanced topics like firmware hacking.


I make the different data for the different serial numbers because I'm kind of paranoid.  I usually go as far as giving the data an expiration date too.  This is mostly because people forget to bring me my stuff back but will remember when it no longer routes them to the fishing hole they're looking for or where they put their turkey blind.  Hahaha!

I've tried the website you attached in your last post.  It still gives me the same message only when I try to assign an expiration date for the data I've created.  If I just leave the expiration date blank for my key generator the maps work just fine but I really don't want to do that if I can get away with it.

I've also tried installing an older firmware that is on the other two units in question that still work just fine with the expiration date added into the key when generated.  But the GPS SW Version is different.  Like, the Garmin Nuvi firmware is the same but then another version number, this "GPS SW Version" is different.  I'm not really sure what the GPS SW Version is. 

The photo I've attached is the information for one of the GPS devices that still works with all the same settings as I've used in the past.  On the right you'll see "GPS SW Version" and it is the only thing that's different between the units.  Both working units are 2.90m while the other three that don't work with an expiration date are 2.20m.  Do you have any idea what this GPS SW Version is?  I have a couple of theories but haven't really found much through different forums to help me understand what this does to the device or if it's even something I should really be considering at all to help me come to a solution.

I've been doing this for about 10 years also.


My understanding is that the "GPS Software" is the low level firmware for the GPS chipset itself. I don't know why that would affect anything in a map, but it's possible. No experience with creating locked maps.

What is a "key generator"? That sounds like the kind of hacker tool that some people have used to illegally crack Garmin's maps. If so, then the management of this site would not approve of any discussion.


Key Generator.exe is an application I downloaded off the internet that I use in conjunction with Sendmap20 to create my GMAPSUPP.IMG when making the mapping data I use in the units we have been discussing but I think I figured something out.  I made the end date like if the unit was just pulled out of the box brand new 1023 weeks ago and that seems to have solved my problem.