Got a 300ci fresh out of the box that pops up with a C5102. Rotated main charge rollers between cyan and magenta drum assys and it comes up with C5104 which is for yellow even though we didn't touch the yellow main chge. Thinking we may have to replace the MHVPCB but nasty job so suggestions would be welcome. We tried reseating drum units and MHVPCB connectors
but no joy.

Just an update. The MHVPCB was replaced and the C5102 is still there . Disappointing after that job. Rotated drums around but still getting code. Area rep had us check for pinched wires to left of image formation holder but they're good. Any suggestions?

Final update. Had the regional rep in with a potpourri of boards and the engine PWB was the culprit. So much for quality control.

Thanks for posting this Protec. I had the same code on a 300ci and went down the same gruelling path that you did with the MHV board; whew.
The KMA support hotline escalted to my region rep who was on vacation. Thanks to your post, I convinced my owner to order an engine board and it fixed the problem same as you.

Wow, I wish I had the luck you guys have had. I've had this issue three times. The first two the culprit was the high voltage pwb. The machine that has it now (which I am standing in front of as I type this) has had the drums and chargers replaced by two other techs over the last months, all of this after an engine board was replaced 3 months prior bc of an F code. Now I have inherited this mess and it's looking like the high voltage again. I'm hoping since this machine has had to many issues they will send me both an engine and a hvpwb.