[Error Code] Minolta bizhub c451 error code: c2204

[glrfutures]

I replaced the waste toner box, checked that M20, and gears were turning. I performed the reset procedure, but the error code returns. The copier briefly recycles, and the error code returns. Just before the message appears, there is a ratcheting sound like a gear is grinding. I can't enter service mode from the error code to check sensor. This is my first encounter with this model; the service manual for this machine is weak, and any help is appreciated.

Thanks, glrfutures