Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Gain access to PCB (use Insulation Mat as required)
Hot water temperature selector to OFF
Disconnect connector X2 from PCB

Measurement:

Measure resistance across connection 1 and connection 3 (pink wires) on connector X2 on the main PCB.
Resistance should be open circuit.