whirlpool duet - what needs to be replaced

Washer Repair
1

Our whirlpool duet washer has stopped working, displaying an error code
of F71 and later after power off and on F70. Even later, after power off and on, no error code was displayed and tried to run it. The detergent dispenser
worked and a bit of water came in and then error code again, but this time
got F28. Also tried running diagnostics on as given on the green sheet inside
the washer - result starts to go, door locks, displays C00 (though I had to press prewash a couple of times to get this) then finally after some time
(minutes) F28 is displayed. (this is serial communication error between
CCU and MCU).

So my question is : should I replace User Interface, CCU, or MCU or some
subset of those? Or should I do something else?

2

[SIZE=2][FONT=Swiss721BT-RomanCondensed][SIZE=2]1. Check for continuity of the User Interface harness.[/SIZE][/FONT]
[FONT=Swiss721BT-RomanCondensed][SIZE=2]2. Check wire harness connections to the User Interface and[/SIZE][/FONT]
[FONT=Swiss721BT-RomanCondensed][SIZE=2]the Central Control Unit.[/SIZE][/FONT]
[FONT=Swiss721BT-RomanCondensed][SIZE=2]3. Replace User Interface if drum is rotating.[/SIZE][/FONT]
[FONT=Swiss721BT-RomanCondensed][SIZE=2]4. Replace Central Control Unit if drum is not moving.[/SIZE][/FONT]
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