Failure-detecting device for air-fuel ratio sensors of internal combustion engines

摘要

A failure-detecting device detects failure of an air-fuel ratio sensor arranged downstream of a three-way catalyst in an exhaust passage of an internal combustion engine. The air-fuel ratio of an air-fuel mixture supplied to the engine is perturbed with a predetermined repetition period and by a predetermined amplitude. There is detected an amount of change in an output from the air-fuel ratio sensor responsive to the perturbed air-fuel ratio. Failure of the air-fuel ratio sensor is detected based on the amount of change in the output from the air-fuel ratio sensor.