Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to DC Volts Set meter to measure DC Volts
Turn Hot Water Tap On
Gain access to PCB (use Insulation Mat as required)
DHW flow rate greater than 3 ltr/min
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Measurement:

Measure DC voltage across pin 6 (yellow wire) connector LV2 and a suitable earth connection.
Expected voltage should be between 2.0 - 3.0 VDC.