Set Appliance State:

Mains Power Off
Ensure primary heat exchanger is below 40°C (to ensure a demand for preheat)
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?
The pump fitted might be an ErP.
Note:
Do not take sound or vibration as a sign of the pump running.