Abstract: An aged exhaust gas oxygen sensor (EGO) simulator is inserted between an exhaust gas oxygen sensor and an electronic control module for testing the response of fuel control and emission systems to various amounts of exhaust gas oxygen sensor aging/degrading. The sensor signal is input to a summing amplifier where a delay signal is added. Positive and negative summing amplifier outputs go through vernier and decade controls, which add delay, and then to a variable gain inverter. The difference signal is integrated and output to the summing amplifier as the delay signal and output to a ground offset control for shifting the waveform up and down before going out to the control module. The vernier and decade controls add delays to mimic an aged/degraded exhaust gas oxygen sensor.

Abstract: A method of controlling the operation of heaters for an exhaust gas oxygen sensor as function exhaust gas temperature as compared to a first exhaust gas temperature to turn on the heaters and a second exhaust gas oxygen sensor temperature to turn off the heaters.

Abstract: Air/fuel ratio in an internal combustion engine is controlled so as to test the operation of an exhaust gas oxygen sensor. The engine is divided into two banks, each bank including an intake bank of cylinders, an exhaust path, and an exhaust gas oxygen sensor in the exhaust path. Air/fuel ratio control signals are used in connection with each of the two banks, the control signals being 180.degree. out of phase with each other.

Abstract: Method and apparatus for controlling ignition timing during alternating rich and lean fuel-air composition excursions for efficiency and for controlling torque fluctuations associated with the excursions. The method, for use in a vehicle having an internal combustion engine including an electronic fuel and spark control module, includes reducing spark advance instantaneously during a rich fuel-air excursion, and increasing spark advance during a lean fuel-air excursion. The amount of spark advance adjustment is preferably determined utilizing nonlinear functions which relate spark, torque ratios, and air-fuel ratios.

Abstract: A system for detecting a fault in an exhaust gas oxygen (EGO) sensor includes generating a first signal with a first voltage if the EGO sensor output signal is approaching an unacceptable voltage and a second voltage if the EGO sensor output signal has an unacceptable voltage. The system further includes setting a first flag if the first signal has the first voltage and a second flag, indicating an EGO sensor fault, if the first signal has the second voltage and the first flag is set.

Abstract: Functionality of the exhaust gas oxygen sensor is determined by continually monitoring the exhaust gas oxygen sensor voltage to determine both a peak rich voltage and peak lean voltage. Based on the information after some predetermined time period, a system determines whether rich air/fuel ratio excursions are required and lean air/fuel ratio excursions are required. If a rich air/fuel excursion is required, then there is a command to decrease the air/fuel ratio to make it rich until the peak rich voltage is greater than a predetermined threshold voltage. Analogously, if a lean excursion is required, then there is a command to have a lean air/fuel ratio excursion done until the peak lean voltage is less than a predetermined threshold. If a time out happened before the peak rich voltage was greater than the rich threshold or the peak lean voltage was less than the lean threshold, then there is a determination that there is a malfunction detected on the sensor/circuit.

Abstract: Method, for controlling fuel supply to an internal combustion engine utilizing a modulated air-fuel signal having a modified square-wave waveform, of monitoring operation of an oxygen sensor for sensing engine exhaust gas oxygen level. The method includes generating the modulated air-fuel signal having the modified square-wave waveform designed to produce a particular engine exhaust response for interrogating the oxygen sensor, and operating the engine based on the modulated air-fuel signal. The oxygen sensor produces an associated output signal in response to sensed exhaust gas oxygen levels. The method also includes processing the output signal of the oxygen sensor associated with the particular engine response so as to determine the operating condition of the oxygen sensor and to verify acceptable test conditions.