Patent ID: 6287453
Filing Date: 2001-09-11
Classification: F02D,G01N

Abstract:
A method for diagnosing a lambda probe disposed upstream of a catalytic converter of an internal combustion engine producing an air fuel coefficient (.lambda.), the lambda probe having an amplitude gain and outputting an output signal having a continuous characteristic curve with respect to the air fuel coefficient (.lambda.) received as an input variable of a lambda control loop, the method which comprises:superposing a periodic forced stimulation at a prescribed frequency and amplitude on a required value for an air-fuel ratio;simulating a system response of the lambda control loop to said superposing step with a model having a sensor delay time as a model parameter, the model having an amplitude gain;determining the amplitude gains of the model and the lambda control loop and performing a comparison of the amplitude gains with each other;performing a modification of the model parameter, the sensor delay time, in accordance with a result of the comparison of the amplitude gains; andclassifying the lambda probe as defective if a value of the modification of the model parameter exceeds a prescribed threshold value.