Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
CH Demand
Gain access to PCB (use Insulation Mat as required)
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure the voltage from the brown wire in the 8 way plug on the PCB to a suitable earth point.
Mains voltage should be present.
Voltage will only be present during the sparking phase of the ignition sequence.
Note:
Ensure a good connection is made to avoid misdiagnosis.