Garmin fixes the Fenix 8 heart rate failure with update 23.40

If your Fenix 8 suddenly forgot how to measure heart rate, this is the update you need. Garmin has started rolling out software 23.40, with an official fix for the optical heart-rate sensor failure reported after version 23.39. 

So far the rollout has only reached 20% of users. So plenty of owners will not see the update yet.

Garmin finally names the problem

Garmin’s changelog is unusually direct about the main fix. It says version 23.40 fixes the optical heart-rate sensor not working, which is a much clearer acknowledgment than the troubleshooting advice affected owners had been receiving.

This was not a case of slightly inaccurate readings during a run. On affected watches, the green and red sensor lights went completely dark and wrist heart rate disappeared, including during recorded activities.

That also created a knock-on problem for the health data built around the optical sensor. Owners reported losing overnight HRV, Pulse Ox, sleep information and Body Battery data, turning an expensive multisport watch into a far less useful device until the sensor came back to life.

The earlier fixes were all over the place

We first reported the Fenix 8 heart-rate failure on October 3. Some owners managed to recover the sensor after switching the watch off for more than 90 seconds, while others needed a factory reset or firmware reinstall.

Those methods were never dependable. In some cases the sensor returned only to stop again, while other watches remained without heart rate after every suggested reset and reinstall.

Garmin support even told one owner that the watch might need replacing if reinstalling the software failed. Version 23.40 now confirms that Garmin had a software fix to make, so affected users should install this release before treating the sensor as failed hardware. 

The timing also adds another corrective release to a fairly untidy stretch of Fenix software. Garmin previously had to issue version 22.44 after display complaints, and 23.40 arrives only a few weeks after the much larger 23.39 update.

There are three other changes

Heart rate is the headline fix, but it is not the whole changelog. Garmin says 23.40 also fixes a crash when users enable active heart-rate broadcasting through Garmin Connect Mobile, along with a problem that allowed notifications to make noise while silent mode was enabled.

The final entry simply mentions other minor issues, without explaining what they are. This is still a compact hotfix rather than another feature release, so owners should not expect new training tools or interface changes.