Set Appliance State:

Set Multimeter to DC Volts Set meter to measure DC Volts
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure for DC volts between pin 3 on connector X2 and an earth connection (use the copper pipe to the gas valve as earth).
Expected voltage approximately 4.8 Vdc.
Is the voltage measured as expected?
Note.
Ensure a good connection is made or misdiagnosis may occur.