Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Gain access to PCB (use Insulation Mat as required)
Disconnect external controls from connector CN5 & make safe
No demands
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

With external controls disconnected does the boiler still attempt to fire after self-check & purge cycle has completed?
Cancel the purge cycle if required as per previous test.