Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove the 3 wire connector from the fan
Remove connector X4 from the PCB

Measurement:

Test 1:
Measure the resistance between pin 1 on X4 and the brown at the fan connector.
Expect continuity / zero resistance.
Test 2:
Measure the resistance between pin 2 on X4 and the blue at the fan connector.
Expect continuity / zero resistance.
Also visually inspect the condition of the harness and its connectors.
Is the harness in good condition and are the resistance readings as expected?