Set Appliance State:

Mains Power Off
Set Multimeter to DC Volts Set meter to measure DC Volts
Turn Hot Water Tap On
Selector switch to Water
Run DHW boiler until water runs cold before turning mains power on
Gas On
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow fan to run and boiler to ignite.
Measure voltage between the two yellow wires on the modureg solenoid.