Set Appliance State:
Set Multimeter to Resistance 
Isolate Mains Power to appliance as per TOPs P4
Disconnect fan harness from the fan and PCB
Disconnect fan harness from the fan and PCB
Measurement:
Check for continuity (zero resistance) between the ends of each of the 5 wires between the fan and the PCB.
Also inspect the harness for good overall condition.
Also inspect the harness for good overall condition.
Isolate as per TOPs P4
and refit as necessary