Is this a 600, 750, or 1000?
John may know better but as I understand it, the TOS only produces a FI error (C23) if the sensor is producing an out-of-spec voltage. If it's in a tip-over state but otherwise functioning normally, the engine will turn off without an error. So make sure that the TOS hasn't come off its mount.
It's fairly easy to rig up an indicator light to tell if the ECM is losing power. You can run leads from the O/W and B/W leads on the dealer mode connector forward to a 12 V LED located somewhere around the cluster. This doesn't have to be pretty, just use some duct tape to hold things in place. If the light goes out, the ECM is somehow losing power. That normally would be related to the interlock relay or kickstand switch. If the light stays on but the engine dies, that's normally due to the fuel pump losing power; either it's bad or isn't getting power (bad electrical connection or ECM is turning it off). You could move the LED over to the fuel pump relay (Y/R lead) to check that out. But you'll have to find somewhere for a ground connection, which could be the dealer mode connector.
Last edited by billv; 09-06-2019 at 12:30 PM.