Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect X20 from the pcb
Disconnect the fan connector from the fan assembly

Measurement:

Measure the continuity of the following leads on connector X20 16(blue), 17(red), 3(black) and 4(grey) to the corresponding lead on the fan connector.
Expected resistance continuity, zero resistance.