The F28 code is a comm failure between the MCU and the CCU. First, check the wiring harness connections to the MCU, the Motor, and the CCU. Make sure all the connections are tight and there are no ground wires off. Then check the connections of the CCU board within the housing.
Yes, I read a couple past members that diagnosed it as the MCU being the cause more than the CCU.
So you can order the MCU and/or the CCU, then I'd install the MCU first to see if that fixes it. ALL PARTS YOU ORDER THROUGH OUR LINKS COME WITH A 365 DAY FULL REFUND, EVEN IF YOU INSTALL THEM AND IT DOESN'T FIX IT.
You may also want to remove the MCU board from its plastic casing, and look for burned/arc spots on it, we've had a few members report that. If you find yours does, just order the MCU.