Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Ensure plug has been refitted to water pressure switch
(take care as plug can be fitted incorrectly)
Disconnect CN102 from the control PCB

Measurement:

Measure the resistance between pins 1 and 2 at the disconnected plug.
Resistance should be short circuit (zero resistance).