Just for the record, We've just had the exact same fault on our 2008 KX-S AWD. Warning lights came on a couple of months ago, reset by dealer, who said it was a one off glitch. Then last week the lights lit up again. The dealer has replaced the O2 sensor (after initially diagnosing a bad earth on the sensor, and cleaning the contacts, then the fault re-occured). It seems ok now, so hopefully that is the end of the problem. Very happy with the dealer response (CMI Toyota_Adelaide) Anyone else had this fault?