Set Appliance State:

Mains Power Off
Turn Hot Water Tap On
Set flow rate to 2.8 litres a minute
DHW temperature set to MAX
Selector Switch in Hot Water Position
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance if it is in lockout.
Does the pump run with a DHW demand before fault reoccurs?