Set Appliance State:

Mains Power Off
Turn Hot Water Tap On
Main On/Off Control in the On position
Heating Control to Hot Water Only
CH Temperature Control to Maximum
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 Diagnostic Mode on Multifunction Display by pressing both buttons together.
Push left hand button to step through diagnostic codes until screen shows "d.35" and
then press the right hand button once. The display should now show "1".
Reset Display.