Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to AC Volts Set meter to measure AC Volts
Turn Hot Water Tap On
Remove connector CN2 from the PCB and make safe
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Reset the appliance if required.
(Press reset button once then release)
Allow the fan to run and the ignition sequence to commence.
Measure for mains voltage between pin 1 on connector CN2 (where the gas valve connector was fitted) on the main PCB to connector N (blue) on the mains terminal block.
Expect mains voltage.
Note.
Mains voltage should be present for approximately 5 seconds, this will then be present again after approximately 25 seconds. This will be repeated 3 times before lockout occurs, reset as required until test is complete.