Page 109 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

Toyota Motor Co. Ltd. 91

3) calculating an area surrounded by the output signal response curve of the upstream airhe1
ratio sensor and a predetermined reference value line
4) forming the ratio of the two areas
5) determining whether or not the three-way catalytic converter has deteriorated in accordance
with said area of step 2 or ratio of areas of step 4 when the signal condition detecting means
detects that the output signal of the downstream airhe1 ratio sensor is being maintained at
either said rich side or said lean side air/hel ratio for more than said predetermined time.

:normal catalytic converter
------ :deteriorated catalytic converter
1-

v2
'stoichiometric
0 time airffuel ratio
/
v2 0 1-L
1

Volts

time

Fig. 44 (fiom DE4234 102)