So it finally got above 40 degrees fahrenheit here over the weekend and my testbook icon did not come on! It's been on most of the winter - but all the functions of the climate control seem to work properly. I tried fresh/interior air - all the position settings for the vents - temperature of the air seems consistent side to side - everything and it all works properly, but I still had a testbook. So I changed the cabin air filters and the plenum filter - STILL had a test book. Then over the weekend the temperature rose to the 50's or so - that combine with the sun and a sunroof with the shade open and the interior was fairly warm - I drove it for over 2 hours solid and no testbook. Then, back in the 30's today and the testbook is back. IDEAS?