Engine air/fuel control system with catalytic converter and exhaust gas oxygen sensor monitoring

摘要

An engine air/fuel control system is shown (300-428) responsive to a feedback variable derived (410-428) from an exhaust gas oxygen sensor (16) positioned upstream of a catalytic converter (20). A non-catalytic exhaust gas oxygen sensor (24) having a non-catalytic electrode (490) positioned in the engine exhaust downstream of the converter (20) is coupled to a current pumping circuit (28). Current is pumped into an electrode of the downstream sensor (24) shifting its output step change towards richer air/fuel ratios. Pumping current is gradually increased in amplitude until the downstream sensor (24) incurs a change in its output state (602-634). The pumping current occurring at the time of such change in output states provides a measurement of catalyst efficiency.