US 6,604,007 B2Granted

Test method for verifying correct matching of an exhaust gas oxygen sensor and a vehicle engine

AssigneeGeneral Motors Corporation

InventorsMartin Leven, William J. Morgan

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Abstract

An improved assembly method and a corresponding diagnostic method carried out by an electronic engine control module in a factory test setting reliably and inexpensively verifies correct matching of a vehicle engine and an exhaust gas oxygen sensor installed on an exhaust pipe thereof. Heating elements within the oxygen sensors are manufactured so as to exhibit an electrical resistance that is different for each type of sensor. Due to normal part-to-part tolerance variation, the heater resistance of one type of oxygen sensor falls into a first range, and the heater resistance of the other type of oxygen sensor falls into a second range. The electronic control module for each engine is calibrated as part of its overall fuel control calibration, to recognize an oxygen sensor current requirement range corresponding to the respective fuel control (i.e., leaded or unleaded). The electronic control module operates during an initial period of engine operation during factory testing prior to convergence of the first and second resistance ranges to measure the average current supplied to the installed oxygen sensor, and to compare the measured current with the calibrated current requirement range. The comparison is used to set a diagnostic indicator, which is checked to determine if the engine should be directed to the next assembly area or returned to a repair area so that the correct sensor may be installed.

A test method for verifying correct production of engines having first and second fueling characteristics, wherein fueling of each of the engines is controlled by a respective electronic control module, wherein engines having the first fueling characteristic are designed to be equipped with a first type of exhaust gas oxygen sensor, and engines having the second fueling characteristic are designed to be equipped with a second type of exhaust gas oxygen sensor, and wherein each such exhaust gas oxygen sensor includes a heater element that is supplied with electrical current by the respective electronic control module during operation of a respective engine, the test method comprising the steps of:

specifying an electrical resistance of the heater elements of said first and second types of exhaust gas oxygen sensors such that the electrical resistance of heater elements for the first type of exhaust gas oxygen sensor fall in a first range, and the electrical resistance of the heater elements for the second type of exhaust gas oxygen sensor fall in a second range;
storing a calibration parameter in the electronic control module for each engine, where the parameter stored in engines having the first fueling characteristic corresponds to said first range of electrical resistance, and the parameter stored in engines having the second fueling characteristic corresponds to said second range of electrical resistance;
starting a produced engine equipped with an exhaust gas oxygen sensor;
detecting an electrical current supplied to the equipped exhaust gas oxygen sensor by the respective electronic control module;
comparing the detected electrical current to the calibration parameter stored in the respective electronic control module;
and
indicating that the equipped exhaust gas oxygen sensor matches the produced engine if the detected electrical current matches the stored calibration parameter, and that the equipped exhaust gas oxygen sensor fails to match the produced engine if the detected electrical current does not match the stored calibration parameter.

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Abstract

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