HO2S Sensor 2

The scan tool range is 0-1000 mV. The HO2S Bn1 Sensor 2 parameter is the post-catalyst exhaust oxygen sensor output voltage. Voltage should fluctuate within a range between about 50 mV (lean exhaust) and 800 mV (rich exhaust) while operating in Closed Loop. The post-catalyst HO2S output voltage will fluctuate slowly over a longer period of time, compared to the fuel control HO2S. This is due to the oxygen storage capability of an efficiently operating catalyst. If the voltage is fluctuating rapidly, and the catalyst is hot, low catalyst efficiency may be the cause.