Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Ensure gas valve connector is re attached to gas valve
Remove connector M7 from the PCB

Measurement:

Test 1:
Measure the resistance between pin 22 on connector M7 and a suitable earth.
Expect a reading of 1 Mohm or greater.
Test 2:
Measure the resistance between pin 23 on connector M7 and a suitable earth.
Expect a reading of 1 Mohm or greater.
Are the resistances as expected?