Set Appliance State:

Mains Power Off
Set Multimeter to AC Voltage Set meter to measure AC Volts
CH Demand
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Remove both the spaded white and blue wires from gas valve 2 solenoid, noting their positions and measure the resistance across the solenoid.
Resistance should be approximately 2 K ohms.
Replace wires after test.