Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Gain access to PCB (use Insulation Mat as required)
Remove connector X20 from the PCB

Measurement:

Test 1:
Measure for resistance across pins 9 & 18 (green leads) of connector X20.
Expected resistance approximately 54.0 Ohms.
Test 2:
Measure the resistance between pin 9 on connector X20 and a suitable earth.
Expect a resistance of 1MOhm or greater.
Are the resistances measured as expected?
Note.
Ensure a good connection is made as misdiagnosis will occur.