Set Appliance State:

Mains Power Off
Ensure primary heat exchanger is below 40°C to ensure a preheat demand
(If the fault on the appliance does not allow the heat exchanger to cool to below 40°C, then this can be done manually by draining the boilers primary heat exchanger and then refilling)
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

If required reset appliance
(press and hold reset button for 5 seconds, then release).
Turn ECO mode OFF
(press and hold the ECO button until it is no longer illuminated).
This turns the pre heat function ON.
Does the pump run with a preheat demand?
Note:
Do not take sound or vibration as a sign of the pump running.