This blog entry will be the final update on my Garmin Forerunner 405cx problems.
My Forerunner 405cx software issues were not fixed by performing a master reset on the watch. A master reset basically wipes out all pre-existing settings and history, and then reloads the software, including the latest software update.
After performing the master reset process late last week, my 405cx is still functional and the battery does hold a charge. The problem is I cannot tell how much battery life is left on the watch. The software “battery gauge” reads either 100% or 0%, whereas in the past it would give me the remaining percentage charge life on the battery. I run four times a week, so I make sure my watch is fully charged before I head out for a run. When the watch is hooked-up to the wall charger, you’ll notice the watch screen reads either “charging” or “complete”. I’m good to go when I see “complete”.
So, my watch functions, but not how it was designed to function.
If you’re interested, below you’ll find the master reset procedures – keep in mind a master reset will erase all saved data on the Forerunner watch. .
Here’s the Master Reset process:
- Press and hold the “start/stop” and “lap/reset” buttons simultaneously
- Keep both buttons pressed for 8 seconds or until the screen goes blank
- The release the “start/stop” button and continue to hold the “lap/reset” button for an additional 3 seconds
- Release the “lap/reset” button
- Select the Enter (“start/stop”) button to clear user data
After this sequence, you’ll follow the set-up prompts and re-set your profile options.

Hi Fred,
Thanks for the update and follow up. A couple of quick questions: How long are your runs – in other words, even though you can’t tell how much charge remains in the battery, would the watch last for a 5 hour run? Secondly, I don’t understand the need for depleting and recharging the battery after the master reset. I assume the master reset doesn’t deplete the battery, but the discharge and recharge is to reset the battery indicator?
Thanks once again for your assistance – I guess I will be doing a master reset as well, since my battery is not holding charge at all well.
Cheers,
Vernon
Vernon….I’m just passing on the master reset process as recommended by the Garmin Tech folks. I’m afraid I can’t explain the technical reasoning behind the battery depletion and recharge. I recommend calling the Garmin Tech team at 1-800-800-1020. Perhaps they can provide a clear technical explanation.