Patent ID: 7114326
Filing Date: 2006-10-03
Classification: F01N,F02D,Y02T

Abstract:
1. A diagnostic apparatus for diagnosing a deterioration state of a catalyst in an engine, comprising: a memory for storing a preset criterion value and a predetermined range for a state variable of the engine that correlates with a physical quantity affecting a catalytic action of the catalyst; and a processor operatively connected to the memory for obtaining an index value indicative of a conversion efficiency of the catalyst, receiving a value of the state variable of the engine, suspending a determination of the deterioration state of the catalyst if the value of the state variable is outside the predetermined range, and determining the deterioration state of the catalyst by comparing the index value with the preset criterion value if the value of the state variable is within the predetermined range, wherein the processor gives the index indicative of the conversion efficiency of the catalyst based on signals received from a first oxygen concentration sensor provided upstream side of the catalyst and a second oxygen concentration sensor provided downstream side of the catalyst.