Set Appliance State:

Mains Power Off
Set Multimeter to AC Voltage Set meter to measure AC Volts
Turn Hot Water Tap On
Boiler Operating Switch / Programmer set to WATER only
Gas On
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

Allow fan to run and pilot to ignite, measure the voltage across connection ML (Brown wire) and connection MN (Blue wire) on connector CN3 on the sequence control PCB.
Note:
On some models sequence control PCB may only have numbered connections in which case connections 11 and 12 will be used for test.