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 the resistance between pins 1 & 9 on connector X20.
Expected resistance approximately 44.0 Ohms.
Test 2:
Measure the resistance between pin 1 on connector X20
and an earth connection (use the copper pipe to the gas valve as earth).
Expect a reading of approximately 1 MOhm or greater.
Are the resistances measured as expected?