Set Appliance State:

Mains Power Off
CH Demand
Main On/Off Control in the On position
CH Temperature Control to Minimum
Gas On
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

If a fault code is displayed press boiler 'Reset' button.
Select Status Mode on Multifunction Display by pressing right button once.
Remove CH demand and monitor boiler status on display. The correct sequence of events with explanation is shown below.
"S4" (burner operation)
"S5" (fan and pump overrun)
"S7" (pump overrun)
If sequence is correct - Reset display.
If sequence is incorrect note display.