Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect the speed control
(right hand plug) from the pump

Measurement:

Check for continuity (zero resistance) between the ends of the blue and brown wires running between X23 and the PCB to the disconnected plug.
Inspect the harness and connectors for good overall condition.