My Check Engine light came on recently but I don't know what codes came up but the mechanic did indicate that it was an out of tolerance indication on the O2 sensor. Since it was reading (although out of spec) he didn't think the sensor was bad. He replaced the airfilter and cleaned the MAS (Mass Airflow Sensor) and reset the light. So far (600 miles) the light hasn't come on again.

BTW - the engine was knocking horribly any time you stood on the gas but the above "repair" took care of that too.