Had this issue once a few months ago, check engine light turned on and the engine cut out while riding at ~60mph, pulled over and it started back up no issues for the rest of the day. Then it happened again a few days ago, same thing, check engine light comes on engine cuts out, this time it sputtered itself back to life and was misfiring, pulled over and it started up fine with no issues. I unhooked the battery when I got home, went to start it and the starter just turned and never started, bike backfired louder than ive ever heard it, then started next try no problem. Yesterday was the next time i rode, was on the freeway and i felt the engine cut out for a split second, so i was fully ready to pull over and do the whole song and dance again, but this time it was fine, didn't sputter, didn't fully die. No issues for a few more miles when i was rolling up to a stop light, pulled the clutch and stopped, dash was acting like i was still at idle rpms but the engine was shut off. No check engine light, no change in anything on the dash just the engine was off. Rode for 3 more hours after that without a single issue.

stopped at harley and bought a systems relay today just incase that was the issue, and also pulled the codes.

P0151- rear oxygen sensor low
B1155 - neutral switch input short to battery
U1016 - loss of ECM serial data

Bike has a thundermax tuner, intake, exhaust, cams.

anybody have any ideas? Really takes the fun out of riding with that in the back of your mind.

 

The big connection on the TMax is critical. Look for any bent pins, clean it out and when you put it back together make sure it's tight. I use small zip ties to keep it tight.
Check the tuner software for any faults. The TMax likes strong voltage from the battery, so check it and the battery cables, especially the ground to the frame.