I'm in need of some help, it may be something simple and I'm just making it more complicated then it needs to be.

2008 Honda 420FE will only electrically shift into reverse and I can hear the motor try to shift up, the manual shift works as it should. If I manually shift up it will downshift fine with the electric shift, just won't shift up. I took the motor off and housing off and cleaned the gears and greased with no change. I just took off the front case and removed the clutches and everything and found nothing that looked worn or damaged. I cleaned up in there and lubricated everything and reassembled, same issue still present. I'm wondering if the motor isn't turning enough forward or if it's a common sensor issue. Any help or insight would be greatly appreciated!

 

The most logical explanation is the upshift button or wire from it to ECU faulty. I would have expected it to fault code if it tries to work though. Does the gear indicator flash Morse once the fault is on? Another possibility is angle sensor telling ECU that it has changed when it hasn't, as this sensor controls when the shift motor switches off, again faulty angle sensors usually fault code. May be worth trying a new one if it isn't coding though, they are not expensive now as you can get none genuine angle sensors.