Oxygen heater sensor diagnostic routine
First Claim
1. An oxygen sensor heater diagnostic method for diagnosing the condition of an oxygen sensor having a heater and located to intercept the exhaust gases from an engine, comprising the steps of:
- shutting off the heater;
preventing the exhaust gas of the engine from heating the oxygen sensor;
measuring a first output voltage of the sensor at a sensor output as a value V1 when connected to a supply voltage through a large pull-up resistor;
measuring a second output voltage of the sensor at a sensor output as a value V2 when connected to a first predetermined voltage through a small pull-up resistor;
determining an initial delta reference voltage by subtracting V1 from V2;
using said initial delta reference voltage to indicate the sensor internal resistance as of the measurements; and
monitoring the magnitude of the initial delta reference voltage.
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Accused Products
Abstract
A diagnostic method is provided for sensing whether an oxygen sensor is still suitable for use in measuring the fuel-air mixture in the exhaust gases of an internal combustion engine. The method involves turning off a heater of an oxygen sensor when the engine is turned off and allowing the sensor to cool. While the sensor cools, the sensor resistance is measured by means of a large pull-up resistor and a small pull-up resistor, with the small resistor being switched into the circuit at regular intervals for a short period of time. The use of the small pull-up resistor not only increases the reliability of the measurements, but also aids in quickly determining when the sensor resistance has increased above a threshold value indicating the sensor is cool. When the sensor is sufficiently cool, the heater is turned on and the sensor is monitored for a decrease in resistance, indicating that the heater is functioning properly.
47 Citations
23 Claims
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1. An oxygen sensor heater diagnostic method for diagnosing the condition of an oxygen sensor having a heater and located to intercept the exhaust gases from an engine, comprising the steps of:
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shutting off the heater; preventing the exhaust gas of the engine from heating the oxygen sensor; measuring a first output voltage of the sensor at a sensor output as a value V1 when connected to a supply voltage through a large pull-up resistor; measuring a second output voltage of the sensor at a sensor output as a value V2 when connected to a first predetermined voltage through a small pull-up resistor; determining an initial delta reference voltage by subtracting V1 from V2; using said initial delta reference voltage to indicate the sensor internal resistance as of the measurements; and monitoring the magnitude of the initial delta reference voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. An oxygen sensor heater diagnostic method, for diagnosing the condition of an oxygen sensor having a heater and used in an automobile engine to intercept the exhaust gases from the engine and provide a measurement of the fuel-air mixture, comprising the steps of:
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turning off the heater; preventing the exhaust gas of the engine from heating the sensor; measuring a voltage V1 when the sensor is connected through a large pull-up resistor to a first source of voltage and a voltage V2 when the sensor is connected through a small pull-up resistor to a second source of voltage to determine an initial delta reference voltage, that is, the difference between V1 and V2, which is proportional to the sensor internal resistance; repeatedly measuring a first series of delta voltages until the delta voltage exceeds the initial delta reference voltage by a predetermined level; turning the heater on; measuring a second series of delta voltages; comparing the magnitudes of the delta voltages in the second series of delta voltages; and determining the heater is functioning if the delta voltages of the second series of delta voltages are decreasing and determining the heater is not functioning if they are not. - View Dependent Claims (18)
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19. A sensor diagnostic method for diagnosing the condition of an oxygen sensor having a heater, comprising the steps of:
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allowing the sensor to cool; energizing the heater; repeatedly measuring a voltage V1 when the sensor is connected through a large pull-up resistor to a first source of voltage and a voltage V2 when the sensor is additionally connected for a short period of time through a small pull-up resistor to a second source of voltage; determining a series of delta reference voltages by subtracting the repeated voltages of V1 and V2, and monitoring the magnitude of the delta reference voltages to determine whether they are decreasing, as an indication that the heater of the sensor is operating properly. - View Dependent Claims (20, 21, 22, 23)
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Specification