Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove spark generator from gas valve

Measurement:

Measure for resistance across the gas valve connections as per table below:
Gas Valve ConnectionResistance in Kohms (Approx)
Pins 1 & 54.1 Kohms

Note.
Ensure a good connection is made as mis-diagnosis will occur.