Set Appliance State:

Ensure No demands are present
Ensure boiler is cool
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset boiler, press mode and ok for 2 seconds.
Allow the boiler to complete its self-check.
Does the boiler reset?
Note:
If after boiler reset the fault code changes from the original to a different fault code, then CLICK HERE.