Set Appliance State:

Gas Off
Set Multimeter to Continuity Set meter to measure Continuity
Turn Hot Water Tap On
Isolate Mains Power to appliance as per TOPs P4
Boiler On/Off Switch ON
Remove connector plug from PL2 on PCB
WARNING!
ENSURE PLUG IS CLEAR OF PCB.
PLUG WILL NOT BE LIVE BUT PCB WILL BE
WARNING! Mains voltage is expected during test, follow TOPs P4 live testing procedure
Mains Power On

Measurement:

When fan runs check for continuity between connection 4 (Yellow wire) and connection 8 (Yellow wire) at disconnected connector plug.
Note: Measurement taken at disconnected plug not PCB.
Mains Power OFF.
Reconnect plug after test.