Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Gas Off
Set Multimeter to AC Volts Set meter to measure AC Volts
Turn Hot Water Tap On
Disconnect the 2 wire connector from the spark generator
(place in a safe place)
Gain access to the bottom of the PCB
(This may require unclipping it from the main bracket)
Use Insulation mat as required
Note:
Ensure PCB is located safely before turning the power back ON
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow ignition sequence to commence.
Measure the voltage between the 2 way
connector on the brown and blue wires at the PCB.
Expect approximately 160 - 240 Vac.
Note:
Reset as necessary until test is complete.