Patent ID: 6151889
Filing Date: 2000-11-28
Classification: F01N,Y02T

Abstract:
A catalytic converter monitoring method for an internal combustion engine with a first group of cylinders coupled to a first catalytic converter and a second group of cylinders coupled to a second catalytic converter, the method comprising the steps of:measuring a first number of transitions from a first state to a second state of a first exhaust gas oxygen sensor positioned upstream of the first catalytic converter;measuring a second number of transitions from said first state to said second state of a second exhaust gas oxygen sensor positioned downstream of the first catalytic converter;measuring a third number of transitions from said first state to said second state of a third exhaust gas oxygen sensor positioned upstream of the second catalytic converter;measuring a fourth number of transitions from said first state to said second state of a fourth exhaust gas oxygen sensor positioned downstream of the second catalytic converter; anddetermining a degradation of the first and second catalytic converters derived from a combination of a first ratio between said first and second number of transitions and a second ratio between said third and fourth number of transitions.