Set Appliance State:

Mains Power Off
CH Demand
CH temperature control to max
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance, press and hold the reset button until the chimney
sweep button led flashes rapidly, then release the reset button.
Allow the boiler to go through its ignition sequence.
Does the original fault code return (2 flashes red) or does the boiler ignite and operate correctly?
Note:
If after boiler reset the fault code changes from the original to a different fault code, then CLICK HERE.