Set Appliance State:

Mains Power Off
Wait approximately 15 seconds
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

After following the above procedure has the fault code reset?
If the fault code has reset but the boiler now shows a different fault code CLICK HERE
If the L5 / C0 code cannot be reset CLICK HERE
If the code resets but you would like to confirm the operation of the boiler CLICK HERE