Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove the lead from the middle electrode

Measurement:

Measure the resistance between the electrode connector and pin 12 on connector LV1 at the PCB.
Expect continuity / zero resistance.
Is the resistance measured as expected?
Note:
Connector may differ slightly in appearance but this does not affect the test.