Finally got around to going to Auto Zone and have them check the Check Engine Light that I posted several weeks ago. The scanner showed a code of P1153. In their print-out, it talks about several problems of which I don't have a clue. 1.Failed HO2S-21 heater circuit. 2.HO2S-21 signal shorted the ECM ground. 3.Improper oxygen supply to sensor- Check sensor connector and wire. Are we talking about a bad oxygen sensor or something else. I am totally lost as to what HO22S-231 is. What do ya think?