How to test the O2 probes on the Viessmann CI2 boiler.

This is just an update on how to measure the O2 probes on a CI2 boiler. Previously we were giving the wrong information, the attached diagram shows the correct information.

When measuring an O2 probe, be sure to measure between pins 3 and 5 for the heater resistance. You should see approximately 3.0 ohms (not k ohms) when reading between pins 3 and 5.