Citroen C3 instrument cluster failed and u0028 code on machine

Question

Car starts and runs a1 but speedo,rev counter,mileage odometer not working and all warning lights on whilst running. The dash lights up with the interior roof light for 1 minute when i open a door then goes out without putting the key in ignition.
My test machine shows fault U0028 Vehicle communication bus A.
I have purchased a replacement unit { Not fitted yet } as told this could be the fault and is a regular thing on the C3

Thanks