Filter and drain checked and clear of obstructions. Pump tested on the bench and powers up OK but does not appear to receive power at the appropriate part of cycle.
Please advise other possible causes, is this a faulty control board?
Given the uncertainty of diagnosis and cost of the replacement board I called in the local repair guy. The control board was indeed dead but the root cause of failure was unusual. Seems the AC supply to the drain pump had been arcing at the connectors on the pump. The two cables are very close together and separated only by very thin plastic at this point. The arcing had taken out a component on the board.