Page 148 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

130 Methods for Monitoring and Diagnosing the Eficiency of Catalytic Converters

slightly while traversing a point at which the aidfuel ratio I=]. As a result, the period of the
wave form of the right airhe1 ratio sensor in which the rich state and the lean state are
inverted is lengthened. Hence, the influence of the exhaust as shown from the right bank is
eliminated considerably, and therefore the wave form detected by the downstream sensor is
able to show the change at the left bank. Therefore, the catalytic converter deterioration
discrimination can be accurately performed.

right bank airfluel
correction coeff. dither
2( /-

left bank airffuel \= 1
correction coeff.

downstream
airffuel

Fig. 61 (from US52791 14)