Set Appliance State:

Mains Power Off
On/Off Switch OFF
Set Multimeter to AC Volts Set meter to measure AC Volts
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Appliance On/Off switch On.
Reset lockout as necessary.
Allow fan to run, after approximately 12 seconds measure voltage across connection 2 (black wire) and connection 4 (blue wire) on the gas valve.
Note:
Voltage will only be present for approximately 3 seconds if burner does not ignite.