What do I need to fix/replace?

My Diplomat ADP8501 goes through the following rouitine every time, before actually starting the wash cycle (these counts are on the 30 mins, 40ºC programme):
Pump out.
182 pulses with 2 flashing lights
2 second pause
139 pulses with 2 flashing lights
2 second pause
123 pulses with 2 flashing lights
Pump out
Fill and complete programme

I have checked the float switch underneath - the switch is fine and there are no leaks.
I have on several occasions put a couple of kettle-fulls of boiling water in the bottom anf jiggled a small bottle brush through the sensor grille.
I have used Dishwasher cleaner.
I have checked all the component connectors.

Any clues please??