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)
Main On/Off Control in the On position
CH Temperature Control to Maximum
Remove plug X26 from Relay Board and make safe
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

If a fault code is displayed press boiler 'Reset' button.
Measure Mains Voltage across X26 on Relay Board during ignition phase.