I had an issue where my cforce 800 wouldn't start, I check all fuses and made sure everything was tight. The starter sounded strong and everything worked but it wouldn't kick over. I noticed the efi start flashing with a 0337 indicator and found it to be the starter sensor. I removed the sensor located under the left plastic cover removing 3 bolts, I then unscrewed the sensor and cleaned it off, there was some metal shavings or something that once cleaned and reinstalled I checked everything one last time and it started right up.

[2015 Z Force 800 53/Trail EPS]

I have heard of this before..