This is my first post but have 2 (new to us)"07" Polaris quads, a 330 and a 450 sportsman. These are principally used for farm work and occasional riding. Both just got fresh batteries a couple weeks apart and both wouldn’t start or even send power to the starter or lights. There are quite a number of discussions on this subject and the ECM comes up often. In both instances I pulled the ECM plug after some tracing / voltage checks and found a lightly corroded pin / socket which coincidentally (or not) was the same pin, same amount of tarnish & corrosion on each machine. After using a tiny pick like tool to scrape the socket clean and very light sanding of the pin, I reinstalled the plug and amazing, both fired right up? Wonder if these "fixes" were just flukes or does the ECM going bad thing come up just due to a connectivity problem, maybe a single pin and socket. Happy they both fired up and have been fine since.