Patent ID: 6922985
Filing Date: 2005-08-02
Classification: F01N,F02D,Y02T

Abstract:
1. In a motor vehicle having an engine with an exhaust catalyst and an oxygen sensor upstream of the catalyst and an oxygen sensor downstream of the catalyst, a method for detecting whether the catalyst has aged, the method comprising the steps of: while maintaining a total test timer, executing a plurality of test blocks, each test block further comprising (a) periodically obtaining upstream data points from the oxygen sensor located upstream of the catalyst, (b) periodically obtaining downstream data points from the oxygen sensor located downstream of the catalyst, (c) calculating upstream absolute differences between consecutive pairs of said upstream data points, (d) calculating downstream absolute differences between consecutive pairs of said downstream data points, and (e) summing said upstream absolute differences in an upstream accumulator and summing said downstream absolute differences in a downstream accumulator, upon the expiration of said total test timer, adding together values in each said downstream accumulator to arrive at a downstream sum, adding together values in each said upstream accumulator to arrive at an upstream sum, and calculating a ratio between said downstream sum and said upstream sum, whereby an aged catalyst is detected by comparing said ratio to a first predetermined value, and compensating the value in said upstream accumulator by a hyperswitching compensation value chosen according to a filtered air flow rate through the engine.