Self-diagnostic apparatus of air-fuel ratio control system of internal combustion engine

In combination:

• a sensor for detecting an air-fuel ratio within an exhaust gas of an internal combustion engine, said sensor having an output which varies proportionally with the detected air-fuel ratio;
• and
• a self-diagnostic apparatus of an air-fuel ratio control system of said internal combustion engine for self-diagnosing an abnormality of said air-fuel ratio control system which feedback-controls an air-fuel mixture supplied to said internal combustion engine by said output of said sensor, said self-diagnostic apparatus comprising:
• detecting means for detecting a predetermined engine condition change upon which an amount of fuel supplied to said internal combustion engine is greatly changed,
• rate-of-change determining means for determining a rate of change of the output of said sensor upon said detecting means detecting said predetermined engine condition change, and
• abnormality determining means for determining an existence of an abnormality of said sensor on the basis of the rate of change of the output of said sensor determined by said rate-of-change determining means.

In combination:

• a sensor for detecting an air-fuel ratio within an exhaust gas of an internal combustion engine, said sensor having an output which varies proportionally with the detected air-fuel ratio;
• and
• a self-diagnostic apparatus of an air-fuel ratio control system of said internal combustion engine for self-diagnosing an abnormality of said air-fuel ratio control system which feedback-controls an air-fuel mixture supplied to said internal combustion engine by said output of said sensor, said self-diagnostic apparatus comprising:
• detecting means for detecting a change in an amount of fuel supplied to said internal combustion engine,
• timer means for measuring a response time lag until the output of said sensor starts to change after detecting the change in the amount of supplied fuel by said detecting means, and
• abnormality determining means for determining an existence of an abnormality of said sensor on the basis of the response time lag measured by said timer means.

In combination:

• a sensor for detecting an air-fuel ratio within an exhaust gas of an internal combustion engine, said sensor having an output which varies proportionally with the detected air-fuel ratio;
• and
• a self-diagnostic apparatus of an air-fuel ratio control system of said internal combustion engine for self-diagnosing an abnormality of said air-fuel ratio control system which feedback-controls an air-fuel mixture supplied to said internal combustion engine by said output of said sensor, said self-diagnostic apparatus comprising:
• detecting means for detecting an engine condition which causes a large change over a short period of time in an mount of fuel supplied to said internal combustion engine;
• rate-of-change determining means for determining a rate of change as a change in the output of the sensor per unit time by detecting the change in the output of the sensor and a time required for the change;
• and
• said sensor being of a type having the output varying proportionally with the detected air-fuel ratio.