Patent ID: 7624628

Claim:
A method of monitoring oxidation catalyst efficiency with respect to an engine exhaust gas, comprising: receiving by a processor a first signal from a first sensor upstream of an oxidation catalyst and a second signal from a second sensor downstream of said oxidation catalyst, wherein said sensors respond differently to the concentration of NO and NO 2 , wherein the first and second signals comprise a pumping current and the pumping current for NO over the range of 1-2250 ppm varies between 3.1 μA and 17.6 μA and the pumping current for NO 2 over the range of 1-2250 ppm varies between 3.0 μA and 14.5 μA; monitoring a difference in said signals as between said first and second sensors; and determining the efficiency of said oxidation catalyst to oxidize an exhaust gas based upon said difference in said signals as between said first and second sensors.