Set Appliance State:

Mains Power Off
DHW Demand
DHW Selector in Maximum (+) position
CH Selector in Minimum (-) position
ON/OFF Switch in ON position
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Test 1:
Reset lockout as necessary.
Does the burner ignite and establish? i.e. Re-ignition does NOT occur.
(If burner ignites and establishes correctly proceed to Test 2)
Test 2:
Allow burner to run for a few seconds once established then turn hot water tap off and monitor display.
Does burner extinguish without an F61 or F62 fault code?