Patent ID: 6658841
Filing Date: 2003-12-09
Classification: F01N,F02D,Y02A,Y02T

Abstract:
A method for checking a conversion ability of a three-way exhaust catalytic converter disposed in an exhaust pipe of an internal-combustion engine, the internal-combustion engine being operated with an air/fuel ratio corresponding to a conversion window of the three-way exhaust catalytic converter, which comprises the steps of:using an NOx sensor for recording an NOx concentration in the exhaust pipe downstream of the three-way exhaust catalytic converter; and using values of the NOx concentration to determine conversion properties of the three-way exhaust catalytic converter by performing the following steps while the internal-combustion engine is warming up with the air/fuel ratio: forming a sum value of the NOx concentration measured from a beginning of a starting of the internal-combustion engine until a time at which the NOx concentration falls below a predetermined threshold; comparing the sum value with the predetermined threshold; inferring that the three-way exhaust catalytic converter has aged if the predetermined threshold is exceeded; and performing at least one of activating a malfunction indication device and inputting an entry into a malfunction memory if the predetermined threshold is exceeded.