bbbean 

In the past few weeks, my Pioneer power meter has gone from providing a reliable measure of my power output to providing dramatically high numbers. My realistic FTP is in the neighborhood of 300 watts, and it told me this morning's 1.5 hour tempo ride had an average of 360 watts (https://connect.garmin.com/modern/activity/1933740085). Based on riding with power for a few years now, that number seems close to 100 watts too high.
I didn't buy the Pioneer computer with my PM, and use a Garmin 520. I've reset connection to the Garmin, calibrated the PM using the Garmin, and have changed batteries twice, but my power numbers still look more like a TdF competitor's than a cat 4 geezer. Any suggestions on a way to update firmware or reset the PM with my Garmin or my phone?
Road season ends in 2 weeks, and I'd sure like to be able to have accurate power feedback for my last bit of training and the last couple of races of the season. Suggestions?