Patent ID: 6550305
Filing Date: 2003-04-22
Classification: F02D,G01N

Abstract:
An activation diagnosis method for a wide-range type air-fuel ratio sensor, said air-fuel ratio sensor being equipped with an oxygen concentration detecting unit formed of a solid electrolyte and outputting detection signals corresponding to oxygen concentration inside a hollow chamber to which exhaust of an internal combustion engine is introduced, and an oxygen pump unit for pumping oxygen into or out of said hollow chamber by controlling a current being applied to a solid electrolyte wall separating said hollow chamber and the exhaust side of said engine so as to control the oxygen concentration inside said hollow chamber to predetermined oxygen concentration, said air-fuel ratio sensor detecting the current being applied to said solid electrolyte wall to output an air-fuel ratio signal corresponding to the oxygen concentration in the exhaust; said activation diagnosis method comprising the steps of:monitoring an output voltage of said oxygen concentration detecting unit after the starting of operation of said engine; judging whether or not said output voltage of said oxygen concentration detecting unit is fixed to either a value equal to or above a rich-side set voltage or a value equal to or below a lean-side set voltage; and diagnosing that said air-fuel ratio sensor is activated under the condition that a status is detected where the output voltage of said oxygen concentration detecting unit is fixed to either a value equal to or above a rich-side set voltage or a value equal to or below a lean-side set voltage.