Set Appliance State:

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

Observation:

Reset appliance (press reset button for 2 seconds and release).
Does the boiler reset?
Note:
1. If after boiler reset the fault code changes from the original to a different fault code, then CLICK HERE.
2. Reset is confirmed by the display returning to CH set temperature when NO demands are present.