Set Appliance State:

Mains Power Off
Gas Off
Set Multimeter to DC Volts Set meter to measure DC Volts
Selector Switch in HW position.
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure Voltage across connector M11 connection 52
(Red wire) and connection 47 (Black wire) on the main PCB.