Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect M2 from the PCB

Measurement:

Measure the resistance between the blue wires (pins 5 and 7) on M2 connector.
Resistance should be short circuit (zero resistance).
Note:
Ensure old overheat wiring is correctly linked as below.