Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector CN4 from the PCB
Disconnect the connector from the fan

Measurement:

Measure the resistance between pins 1 to 5 on connector CN4 to the corresponding pins 1 to 5 of the fan harness.
Expect continuity / zero resistance on each test.
Also visually inspect the condition of the harness.
Note.
The harness wires should be numbered.