I can confirm that replacing the logic board fixed this error for me. Luckily I had a couple of spare logic boards from old MP830 printers.
Unfortunately after replacing the board, another issue became apparent, and that is that the printer complained "Release the scanner lock switch and turn the power off and back on." The lock switch was not in the locked position though.
I re-plugged all the cables to the logic board, as this had once fixed that error for me. In so doing, I noticed that the ribbon cables were badly worn at the ends of the connectors, and this would no doubt be the result of a lot of plugging/unplugging while diagnosing a previous fault, and this one.
Most of those ribbon cables are a friction fit, meaning that each time you re-plug them, they get worn. Evidently they are not made to be re-plugged many times (cheap cables) and so after a while, many of the ribbons simply don't make connection any more. This resulted in the printer assuming that due to a lack of connection, the lock switch was unlocked. Unfortunately there's not much that can be done to replace the ribbon cables - each one is a different length and width, and getting to the other end of each cable would mean a very lengthy job disassembling both the scanner unit and the duplexing unit. Far more trouble than it's worth!
