Exhaust gas sensor operating temperature detection system

In a fuel management system for an internal combustion engine having an exhaust gas sensor for supplying a control signal to the fuel management control, a detection system for detecting when the temperature of the sensor is at its operating temperature to provide an enabling signal to the fuel management control system, said system comprising:

• an exhaust gas sensor operable at a high sensor temperature for generating a first voltage signal in response to the absence of a predetermined constituent gas in the exhaust gas and for generating a second voltage signal in response to the presence of the predetermined constituent gas in the exhaust gas, said sensor having an internal impedance varying inversely with the temperature of said sensor from a very high impedance at its low, nonoperable temperature to a very low impedance at its high operating temperature;
• an exhaust gas sensor amplifier circuit means electrically connected to said sensor, the output signal of said circuit means normally having a first voltage level when said sensor's internal impedance is very high corresponding to the low temperature of said sensor and said circuit means adapted to switch said output signal between said first voltage level and a second voltage level in response to said first and second voltage signals from said sensor;
• storage means electrically responsive to said first voltage level from said circuit means for storing at a predetermined charging rate a voltage magnitude representing the temperature of said gas sensor;
• storage discharge means electrically connected to said storage means and operable for discharging said storage means at a predetermined discharging rate, in response to said second voltage level from said circuit means;
• temperature reference signal means for generating a threshold voltage level representing the normal operating temperature of said sensor;
• and
• a comparator having one input electrically connected to said storage means and another input electrically connected to said temperature reference signal means, the output of said comparator being an enabling signal when the magnitude of the voltage level of said storage means is greater than said threshold voltage level.