Set Appliance State:
Gas Off
Set Multimeter to Resistance 
CH Demand
Isolate Mains Power to appliance as per TOPs P4
Boiler Switch in OFF position
Remove Red and Blue Leads from solenoid
Boiler Switch in OFF position
Remove Red and Blue Leads from solenoid
Measurement:
Measure resistance across the Pilot Solenoid.
Resistance should be approx 2 Kohms.
Reconnect leads.
Resistance should be approx 2 Kohms.
Reconnect leads.
Isolate as per TOPs P4
and refit as necessary