Set Appliance State:

Gas Off
Set Multimeter to Resistance Set meter to measure resistance
Isolate Mains Power to appliance as per TOPs P4
Selector Switch in mid (0) position
Remove connector J10 from PCB and test at connector.

Measurement:

Connect multimeter to J10 connections 1 (black)
and 2 (blue).
Measure short circuit, press ignition button resistance
is now open circuit.
Connect multimeter to J10 connections 1 (black)
and 3 (red).
Measure open circuit, press ignition button resistance is now short circuit.