Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect connector J2 from the ignition PCB

Measurement:

Test 1:
Measure the resistance between pin 5 (orange) and pin 4 (violet) on J2 connector.
Resistance should be approximately 25 - 50 Ohms.
Test 2:
Measure the resistance between pin 4 (violet) on J2 connector to a suitable earth point.
Resistance should be greater than 1M Ohm.
Test 3:
Measure the resistance between pin 5 (orange) on J2 connector to a suitable earth point.
Resistance should be greater than 1M Ohm.