Set Appliance State:

Gas Off
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
Remove inner casing cover
CH potentiometer set to minimum
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance if it is in lockout.
Allow fan to run.
Can sparking be observed between the two spark electrodes situated at the front L/H side of the burner?
Note:
Sparking will only be present for approximately 10 seconds before lockout will occur. This can be reset by pressing and holding the reset button (flashing) for a few seconds.