Tech assistance 2015 Base

I know trying to diagnose an issue without seeing the vehicle is an exercise that usually ends up having frustrating results, but just wondering if anyone else has had this or a similar issue and what the ultimate cause was to correct it.

The basics:

Vehicle had what appeared to be a loss of voltage while riding, but only lasted a short minute or two. When the vehicle made it back to the garage, the usual once over showed nothing obvious, so the battery was tested. It showed a low charge, and after recharging and a load test was done, it showed up as needing replacement. No problem with that since it was a yellow top that was 7 years old. Replaced the battery, cleaned the cables and rechecked to make sure the cables were tight. Tried to start it, but now the engine didn't turn over, but there was a single "click" from the starter. Rechecked for any loose grounds under the hood, and didn't find any. Just to make sure, took jumper cables to use as a "known good ground" and went directly from the head to the frame rail to verify there was a good chassis ground there. Retested and still no start, just the click. Took it out for a test ride by roll starting it and the voltage loss issue was gone. But this time there was a 65580 12 error code (CPU failure). Since it did run fine, I took that to be a phantom code and possibly from a bad ground. Removed the starter and bench tested it. The starter drive did engage and return, but it didn't have anywhere normal rotation, so figured the starter was bad. Bought a new one (we failed to bench test that one since it was new) and put it in. Tried to start it again and had the same results - the click from the starter. Since there were no factory shims under the starter and the original starter drive teeth looked normal after 50K miles if use, it's probably not an issue of the drive not meshing with the flywheel.

So questions is: Anyone ever have that 65580 12 mil code and if so what was the cause? Are there any either hidden grounds or any "hard to see" grounds that may be the cause of both these issues? I find it hard to believe that there was a bad battery, faulty starter, failed CPU as well as the no start issue happening all at once. Any suggestions at this point would be appreciated.

thanks

No idea. IIf memory serves me well, wasn't that all about a "melted" c/b due to the factory wiring not being able to handle the voltage for the power steering and dash or something? If that wasn't done and there was a "melt down", I wouldn't expect to hear the starter noise as it would be an open circuit. I'll take a look at it over the wekend to see if I see an issue there though, Thanks

Nope. Just trying to be a nice guy to start the year off right

Not yet. I figured if there was ebugh of a power signal to the starter foe it to at least click once, there wouldn't be an issue with any open circuit from a broken wire, blown fuse or relay etc. It;s going to be a cold weekend, so it will be back to basics and troubleshooting back from square one and go from there.

thanks