Set Appliance State:

Set Multimeter to Resistance Set meter to measure resistance
Isolate Mains Power to appliance as per TOPs P4
Disconnect 20 pin plug from the control PCB

Measurement:

Test 1:
Measure the resistance between pins 3 and 5 of the disconnected plug.
Resistance should be approximately 250 Ohms.
Test 2:
Measure the resistance between pins 4 and 6 of the disconnected plug.
Resistance should be approximately 250 Ohms.