Set Appliance State:

Mains Power Off
Gas On; Pilot On
Set Multimeter to AC Volts Set meter to measure AC Volts
CH Demand
Selector Switch ON
Gas Control Knob in Main Burner position
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure voltage across connector CN2 connection 1 (blue wire) and connection 2 (L, brown wire) on the PCB.