Laboratory and Engine Studies of the Effect of Nox on the Response of Heated Exhaust Gas Oxygen Sensors 1999-01-1079

Laboratory studies were performed to examine the effect of NO_x on the static switch point of current (1996 MY) production-type heated exhaust gas oxygen (HEGO) sensors. These sensors are used on vehicles for feedback control of the A/F. Several binary gas mixtures and simulated exhaust gas mixtures were used to measure the static response to NO and NO₂ in the laboratory. The results of the laboratory studies indicate that most of these HEGO sensors completely equilibrate NO, but only partially equilibrate NO₂. To validate this result, engine studies were performed to investigate whether the A/F control point shifts when the amount of EGR is changed. Results from both the laboratory and engine studies are presented.