Mx-3640 C4-00 code

[Hansen88]

Hello, I posted about this before bot it was not the right model, I wasnt the one who went there. The machine is a Mx 3640 and getting this c4 oo code. It only happens when using black and duplexing. If I just run single side black it is fine or if I do color with duplex it is fine. Only when doing black and duplex and happens almost immediate. I have been fighting this for more than a week now. I have upgraded the firmware, replace the ptc , primary and secondary transfer units, TC pwb and pcu pwb. I also tried different durm units incase drum blade dragging.There is probably more I have done that I am not thinking of at the moment. None of this stuff has helped. It has got to be some kind of clue that it only does it when doing black and duplex only but I am not getting it figured out. Just seeing if any of you have any suggestions. Thanks

[Hansen88]

I know this is old but I just wanted to post what the fix was. It was one of the two clutches in the back of the machine that turn the transfer belt cam for black or color. The clutch for the black mode wouldnt hold and the cam would move and cause error.