Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
CH Demand
Attach temperature clamp to flow pipe
Set boiler temperature control to MAX
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow appliance to fire and system to heat.
Monitor the temperature of the flow pipe, as the boiler reaches 75 - 90°C does the boiler
ramp down and maintain temperature or shut down without returning to fault code?
Note.
To speed up the process reduce the heating circuit by turning some rads off.