Importance

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Abstract

A method is provided for monitoring catalyst efficiency in a catalytic converter of a motor vehicle, comprising the steps of: (a) detecting an oxygen level of an exhaust gas from the vehicle's engine by using an oxygen sensor positioned at the outlet of the catalytic converter; (b) terminating fuel flow to the vehicle's engine; (c) detecting a change in the oxygen level in response to terminating fuel flow; (d) determining a time period from termination of fuel flow to detection of the change in oxygen level; and then (e) compensating this time period with respect to an exhaust flowrate, such that the compensated time period is indicative of catalyst efficiency of the catalytic converter. More specifically, the exhaust flowrate is determined from a manifold absolute pressure and an engine rotational speed of the engine. To achieve reliable and consistent results, catalyst monitoring of the present invention is only enabled under preferred vehicle operating conditions. In addition, catalyst monitoring may also determine a second measurement of the catalyst by determining a similar time period for catalyst response once the fuel flow returns to the engine.

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First Claim