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:

Reset appliance as necessary and allow fan to run.
Measure the voltage between the blue and brown wires at CN102 on the ignition PCB.
Mains voltage should be present.
Note:
Voltage will only be present for approximately 6 seconds before boiler goes to lockout, reset as necessary until test is complete.