Importance

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Abstract

The invention is directed to a method for checking the aging condition of a catalyzer by utilizing a lambda probe rearward of the catalyzer. For a transition from lean to rich which takes place within a pregiven time span, a check is made if an overshoot of the probe signal occurs which exceeds a pregiven amplitude. A conclusion is drawn as to the aging condition of the catalyzer from an overshoot when the latter occurs. Transitions between lean and rich and vice versa take place especially during the transition from overrun operation to controlled operation of the engine. Transitions of this kind have large swings of the signals of the lambda probes and this permits reliable measurements. In contrast, conventional methods operate exclusively when the engine to which the catalyzer belongs is lambda controlled. The relatively small signal amplitudes occurring thereby lead to a signal/noise ratio which is considerably poorer than in the methods according to the invention.

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First Claim