Diagnosing system for an exhaust gas recirculation system of an automotive engine

Claim 1

A diagnosing system for an exhaust gas recirculation system having an EGR passage communicating an exhaust pipe of an engine with an intake passage of the engine, an EGR valve provided in the EGR passage, control means for producing a valve operating signal for operating the EGR valve in accordance with engine operating conditions, the diagnosing system comprising means for detecting the position of the EGR valve and for producing a position signal dependent on the position of the EGR valve; trouble detector means responsive to the valve operating signal and to the position signal for producing a trouble signal as an alarm signal when the detecting means produces a position signal of an actual closed state of the EGR valve and the control means produces a valve operating signal representing an open state of the EGR valve, said detecting means is a photoelectric transducer, the photoelectric transducer comprises a photodiode and a phototransistor, said transducer includes a shaft connected to a valve body of the EGR valve, said shaft is movable by movement of the valve body into a path between said photodiode and phototransistor, and said transducer includes a U-shaped holder having said photodiode and phototransistor facing each other on arms of the holder.