Page 173 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

Hitachi Ltd 155

catalytic converter

electrode \
oxygen sensor

catalytic converter

lea d

Fig. 71 (from JP7116469)

The method of EP0719931 (1996) comprises the following steps:
1) detecting a leak of the gases in the exhaust pipe by means of an exhaust gas oxygen sensor
mounted in the exhaust pipe and by means of a specific driving condition of the engine. The
leak detection is based on:
a) a frequency component about a combustion cycle of the output of
the exhaust sensor
b) the output signals of the oxygen sensors mounted upstream and
downstream of the catalytic converter