Patent ID: 6164125
Filing Date: 2000-12-26
Classification: F02D,G01N

Abstract:
An apparatus for detecting trouble in a heater control system for a gas concentration sensor, the heater control system having a heater attached to the gas sensor and heater control means for turning electric power supplied to the heater on and off at a predetermined control duty-cycle ratio, the apparatus comprising:voltage detecting means connected to the heater for detecting voltage across the heater when the electric power is turned on and when it is turned off;current detecting means connected to the heater for detecting electric current flowing in the heater when the electric power is turned on and when it is turned off; andtrouble discriminating means for comparing the four thus detected values of heater voltage and current with four respective predetermined thresholds and detecting the absence or presence and location in the circuit of trouble in accordance with which of the four detected values is different from a normal state.