Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Gain access to PCB (use Insulation Mat as required)
Disconnect switched live (pin1) from terminal block & make safe
No demands
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

With switched live disconnected does the pump still run continuously and / or boiler attempt to fire after self-check has completed?