Set Appliance State:

Set Multimeter to Resistance Set meter to measure resistance
Isolate Mains Power to appliance as per TOPs P4

Measurement:

Disconnect the Red and Black wires (1) from the Gas Valve Stage 2 Solenoid (solenoid 3) and measure the Resistance across the Solenoid.
The Solenoid Resistance should be approximately 125 ohms for SIT valve and approximately 120 ohms for Honeywell valve.
Reconnect wires after test.