I had this issue with the MS contact was engaged I tapped it and disengaged. I replaced the tips and two months later happened again. Tips are not welded but Im thinking the plunger is getting stuck. Any ideas?

CO covers the complete drive circuit.

1. Does the code appear with key on or once you start traveling?
With key on: I would look a the MS contact tips make sure they are not welded. Then trouble shoot the SIT's for the drive circuit.
2. Does the code appear with travel attempted?
If it does not come on till you attempt to travel you should start with the forward/reverse contacts then the cables to the motor and then the motor. Looking for an open or shorted circuit.