Oxygen heater sensor diagnostic routine
US5392643A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 22, 1993 |
| Grant date | Feb 28, 1995 |
| Priority date | — |
| Expiry date | Nov 22, 2013 |
Classification
- Technology area (CPC F)Mechanical Engineering; Lighting; Heating
- CPC primaryF02D41/1456
- WIPO fieldMeasurement
- WIPO sectorInstruments
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.