Garmin 910xt firmware “downgrade”.

Note: This is not an officially sanctioned Garmin method of changing your 910xt firmware and if your watch is bricked in the process, I assume no responsibility (I would however feel terrible about it).

by cary blanco @blanco

Update July 16, 2013

Garmin has posted an update to v2.8 that they claim fixes the bug :

Today Garmin released a software update to correct the issue described below. Please click here in order to view instructions on how to install this latest software to your device. We appreciate your patience and apologize for the inconvenience that this issue has caused.

Update June 13, 2013

Garmin has posted an official response to the issue on their forums :

Please note that our Engineering team have determined a reason for an issue where the 910XT will stop tracking location once transitioning out of an Open Water Swim activity. A fix is being developed that will correct the issue with a software update. Until the software update becomes available the best approach to prevent this problem from occurring is to revert the software on your device to our previous 2.60 release. If you need assistance with reverting the software on your device please contact for assistance. We hope to have a software update to provide to our customers soon but do not have a date to provide at this time. We appreciate your patience and apologize for the inconvenience that this issue has caused.

The Problem

After updating their Garmin Forerunner 910xt up the 2.7 firmware, some owners have found when using it in Multi-Sport mode that has starts with open water swim, the Latitude and Longitude of the segments after the swim (T1, Bike, T2 and Run) will be 0,0 (which happens to be off the west coast of Africa in the Gulf of Guinea). You will not get mile spits or other distance based reminders while it’s happening.

Wow, long swim!

This issue was first reported in the garmin forums. And also reported once, no twice in slowtwitch forums.

This problem affected my 910xt and I’ve got no usable T1, Bike, T2 or Run data from my 70.3 race in San Juan. I tried a hard reset and all of the prescribed methods of resting the unit, but I could’t get it back to working properly in multi-sport mode (with an OWS). I wanted to see if I could bring my unit back to 2.6 and if the problem would go away. Below are instructions for how I brought my unit back to the 2.6 firmware and working the way it’s supposed to.

Binging your 910xt back to the 2.6 firmware “The Walkthrough”

This walkthrough assumes you know how to download and unzip files and find them on your computer. It assumes you can navigate the file system and move files in and out of folders as well as make copies of files. It assumes you can edit a file with a text editor. If you’re not sure you can do this, please do not go any further, or just read the instructions and see if you can handle it. It’s not that hard, but I wouldn’t want someone to ruin their watch because they are not at the level that they can do the above tasks on a computer.

I suggest not doing this on a watch that shipped with 2.7 firmware, I would only do this on a watch that was upgraded to 2.7. (Why? Perhaps that watch has newer hardware that was never designed to run firmware earlier than v2.6).
Update 2012–03–30: users have reported success with this update on units that have shipped with 2.7 firmware

This update (downdate?) will do a hard reset to your watch, you will lose all of your data. Make a note of your Data Screens and anything else you personalized on the unit. We will also do a last sync before we install 2.6

Step 1: Turn on your 910xt. Hit MODE, arrow down to “settings”, hit ENTER. Arrow down to “About Forerunner”, hit ENTER. Note the software version (it should be 2.7) and write down the Unit ID number. Hit MODE three time to page back out of the menu screens.

Step 2: Sync your 910Xt with your computer (this will get any items that you haven’t sync’d to your computer). When then sync is finished and you know all of the data on the watch has been downloaded, power down the watch. be sure your 910xt has a good amount of charge because you do not want the battery to die during the firmware transfer.

Step 3: Download the .rgn firmware file and the .udr updater file

Unzip the folder.
The folder, named “910xt_2.6_update_Aug–30–2012” contains two files:

A Note regarding the above files:
Forerunner910XT_260.rgn was downloaded directly from Garmin, they leave the old firmware on their servers, you just need to know where to look for them.
Updates.udr was reverse engineered from the 2.7 version of the Updates.udr file (I took the 2.7 firmware update file and modified the file size and checksum information for it to work with 2.6 firmware).

Step 4: Navigate to the folder on your computer where Garmin stores its data:

On Mac OS X:
/Users/Your Username on your Mac/Library/Application Support/Garmin/Devices/Your FR910XT UNIT ID/

Mac OS X note: Because the User’s Library Folder is hidden in OS X 10.7 (Lion) and 10.8 (Mountain Lion) you may need to type ⌘N (command-N) for a New Window, then ⇧⌘G (command-shift-G) and then type ~/Library/ in the dialog to go to the Library folder on your machine. After that Navigate to “Application Support/Garmin/Devices/” and find the folder with the FR910XT ID number.

On Windows:
C:\Users\Your Username on your Windows Machine\AppData\Roaming\Garmin\Devices\Your FR910XT UNIT ID\

Windows note: You may need to go to Control panel -> Folder options -> View/Show hidden files, folders and drives, in order to be able to see an navigate to the necessary folder.

Navigate to and open the the folder with the FR910XT ID Number that is inside the Devices folder. Ex: 3847235126

Note: If you have or had another Garmin device there may be more than one folder in the Devices Folder, you need to open the one with the Unit ID that you noted earlier.

I would recommend making a backup of this folder just-in-case, it contains all of your Garmin data.

Step 5: Move the two update files Updates.udr and Forerunner910XT_260.rgn that you downloaded earlier to the this folder (the folder with named the with the Unit ID Number).

Step 6: We need to Edit the GarminDevice.XML file that is in this folder. You will need to Open it with TextEdit on a Mac or Notepad on Windows. Important: DO NOT use Word to edit this file, you must use a text editor, not a word processor.

Line 6 of the file should say:

Edit it to say:

Save the file. This file edit tricks ANT Agent in to thinking that your 910xt is running 2.6 and can take the version 2.6 firmware update that we have added to the folder.

Step 7: You’re done, you can power up the watch and a Sync should automagically start. During the Sync new firmware will get uploaded to your 910xt, it will take a little while (perhaps 10 minutes). When it’s finished, you may need to power the watch off and back on. The watch behave as if it is in first time setup, and ask you your age, weight, if you have a HR monitor etc. Once you get though the initial setup, Hit MODE, arrow down to “settings”, hit ENTER. Arrow down to “About Forerunner”, hit ENTER. Note the software version, it should be at version 2.6. Hit MODE three time to page back out of the menu screens and get training again.

Windows note: You can now to go back to Control panel -> Folder options -> View/Show hidden files, folders and drives, and set to “Hide”.

Unit IDs

Compilation of Unit IDs of affected (*) and non-affected (-) units (the last number or two are obscured for anonymity):
* 384166469x - ANDYOBI1 (garmin forums)
* 384217431x - JKOCH77 (garmin forums)
* 384259117x - PETERTC (garmin forums)
* 38426348xx - JESSNICOLE77 (garmin forums)
- 384301011x - PHILIPSHAMBROOK (garmin forums)
- 384300998x - PHILIPSHAMBROOK (garmin forums)
* 38435979xx - niceguy2561 (slowtwitch forums)
* 384396408x - CMAUZE (garmin forums)
* 384422594x - mrkcham (garmin connect)
* 384427126x - ANDYOBI1 (garmin forums)
* 38446267xx - F1rebird (slowtwitch forums)
* 384483243x - JOSHR9876 (garmin forums)
* 384512675x - KURPAL (garmin forums)
* 384528225x - SCOTT_SOUTH (garmin forums)
* 38461796xx - robgray (slowtwitch forums)
* 38471781xx - jaytee (slowtwitch forums)
* 384723506x - GreatScott (slowtwitch forums)
* 38485898xx - Undies2 (slowtwitch forums)
* 384859056x - tri808 (slowtwitch forums)
* 38488695xx - camtdc (slowtwitch forums)
* 38547513xx - bluefever (slowtwitch forums)
* 38550315XX - Singcoop (slowtwitch forums)
* 38575421xx - rph60 (slowtwitch forums)
* 385761368x - JUMPSERVE (garmin forums) / blanco (slowtwitch forums)
- 38576148xx - MADEUPNAME (garmin forums)
* 38596775xx - ANDYOBI1 (garmin forums)
* 38596775xx - ANDYOBI1 (garmin forums)
* 38625091xx - THEMXHOOP (garmin forums)
* 38625102xx - gswiszcza (slowtwitch forums)

Document History

2013–03–26 Initial writeup
2013–03–27 Added Windows, show hidden files instructions (thanks SCOTT_SOUTH)
2013–03–28 Added Unit IDs of affected 910xts
2013–03–29 Added Unit IDs of non-affected 910xts
2013–03–30 Combined list of affected non-affected units to a single list and made a few small copy changes
2013–03–30 added note about the update working in units that shipped with 2.7 preinstalled
2013–03–31 added intro, added links to garmin and slowtwitch forum posts, added h3 sections, added image of problem
2013–04–02 more unit IDs …
2013–04–05 more unit IDs
2013–04–06 s/effect/affect/g
2013–04–08 Added other document formats and more unit IDs
2013–04–12 lowercased “X”s in Unit IDs, added more unit IDs
2013–04–13 added byline (Garmin please don’t sue me) and more unit IDs
2013–04–15 more unit IDs …
2013–04–17 more unit IDs …
2013–04–23 fixed some spelling & URL errors, added another paragraph for context and a more descriptive heading along with more unit IDs
2013–05–06 more unit IDs …
2013–05–27 more unit IDs …
2013–05–28 more unit IDs …
2013–05–30 more unit IDs …
2013–06–08 a few touch ups
2013–06–13 added Garmin’s official response
2013–06–28 more unit IDs …
2013–06–30 Windows Filepath Fix

This Document is also available in other formats

Markdown (master file):
rtf: 910xt-firmware.rtf
pdf: 910xt-firmware.pdf