| abstract |
The sensor has a current limited oxygen sensor (26) with a oxygen concentration sensing element (34), which outputs a current proportional to the oxygen concentration. A heating device (33) heats the oxygen concentration sensing element. The supply of energy to the heating device (33) is controlled by an electronic control unit (40) having a CPU (48), to activate the oxygen sensor. An elemental resistor detector within the control unit detects the resistance of the oxygen sensing element, from the applied voltage and resulting current, and a diagnosis of the oxygen sensor is made by the CPU in accordance with whether the resistance of the element lies within a predetermined range. If the resistance is below or above this range, it is determined that the sensor has a large or small elemental temp. abnormality respectively. |