a method of filtering an oxygen sensor signal is provided . the method includes obtaining the oxygen sensor signal from the oxygen sensor on a periodic basis . the oxygen sensor signal is then compared to an average oxygen sensor signal value . if the oxygen sensor signal is greater than the average oxygen sensor signal value , a high signal counter is incremented . if the high signal counter is greater than a high signal count threshold , the oxygen sensor signal is forced to a high signal value . if the oxygen sensor signal is less than the average oxygen sensor signal value , a low signal counter is incremented . if the low signal counter is greater than a low signal count threshold , the oxygen sensor signal is forced to the low signal value . the high and low signal count thresholds correspond to a preselected period of time indicating a low or high signal trend within the oxygen sensor signal .