I once left my fitbit in the wash (and then dryer) and was wondering why I was suddenly getting all these "congrats on hitting your steps goal!" alerts on my phone.
If only I could find an "open loop" switch to just disable the engine monitoring. Everything runs fine in open loop mode.
Those would by my main suspects if it works well in open loop mode, knock sensor first.
Its sleep stats are also laughable. It's shown me as sleeping right through the time I was showering and cooking breakfast.