| 摘要 |
PROBLEM TO BE SOLVED: To enable monitoring of a sensor heater and a sensor itself by measuring an internal resistance of a sensor ceramic to be compared with a target value which is obtained as a function of the temperature of an exhaust gas and a heating power of the sensor heater. SOLUTION: The temperature of an exhaust gas, a heating power and an internal resistance (x) of a Nernst's cell of a sensor ceramic, namely, λ sensor are measured and the internal resistance of the λ sensor is determined by a characteristic curve group unit as a function of the temperature of the exhaust gas and the heating power. By a multiplying means 20, the internal resistance is multiplied by a specified coefficient and a target value (y) as the results is supplied to a comparison means 30. Then, a comparison is made to determine whether the measured internal resistance (x) is larger than the target value (y) of the internal resistance thus obtained. When it is larger than the value, an error signal is supplied to an OR element 40, which 40 in turn generates an error signal 50 to be stored depending on the case. An error detection logic means 60 detects a short circuiting to a positive potential UB, a drop in load and/or a short circuiting to the ground and the results are supplied to the OR element 40. |
