Set Appliance State:

Turn Hot Water Tap On
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

If required reset boiler.
Allow ignition sequence to commence.
If a fault code other than "E01" occurs during ignition click HERE.
Does the burner ignite & establish?
Note.
Burner can be observed through window next to ignition electrode, 5 attempts of ignition will occur before lockout, reset boiler as required