# US 10,371,080 B2 · Method and device for inspecting an oxygen sensor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,371,080 B2 - Document ID: US10371080B2 - Status: Granted - Kind: B2 - Application number: 15/604,188 - Filed: 2017-05-24 - Published: 2017-11-30 - Granted: 2019-08-06 - Earliest claimed: 2016-05-24 - Assignees: GM Global Technology Operations LLC - Applicants: GM Global Technology Operations LLC - Inventors: Manuel Franz - Web page: https://patentgrep.com/patent/US10371080B2 ## CPC - F02D 41/222: {relating to the failure of sensors or parameter detection devices} - F02D 41/008: {Controlling each cylinder individually} - F02D 41/0295: {Control according to the amount of oxygen that is stored on the exhaust gas treating apparatus} - F02D 41/1445: {the characteristics being related to the exhaust flow} - F02D 41/1454: {the characteristics being an oxygen content or concentration or the air-fuel ratio} - F02D 41/1495: {Detection of abnormalities in the air/fuel ratio feedback system} - F02D 41/26: using computer, e.g. microprocessor - F02D: CONTROLLING COMBUSTION ENGINES (vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed B60K31/00; conjoint control of vehicle sub-units of different type or different function, road vehicle drive control systems for purposes other than the control of a single sub-unit B60W) ## Abstract A method is disclosed for detecting a malfunction of an oxygen sensor in the exhaust gas system of an internal combustion engine having several cylinders. The cylinders are operated at the same air-fuel ratio and the resultant first output signal of the oxygen sensor is monitored. The cylinders are operated at varying air-fuel ratios and the resultant second output signal of the oxygen sensor is monitored. The first and second output signals are compared to determine whether the oxygen sensor has malfunctioned. ## Claims ### Claim 1 A method for detecting a malfunction of an oxygen sensor in an exhaust gas system of an internal combustion engine having a plurality of cylinders comprising: (a) operating the internal combustion engine such that each cylinder is provided with an equivalent air-fuel ratio; (b) monitoring the oxygen sensor to obtain a first output signal during the operating of the internal combustion engine with each of the plurality of cylinders provided with the equivalent air-fuel ratio; (c) operating the internal combustion engine such that a first one of the plurality of cylinders is provided with a higher air-fuel ratio than a remainder of the plurality of cylinders and a second one of the plurality of cylinders is provided with a reduced air-fuel ratio than the remainder of the plurality of cylinders; (d) monitoring the oxygen sensor to obtain a second output signal during the operating of the internal combustion engine with the first one of the plurality of cylinders provided with the higher air-fuel ratio and the second one of the plurality of cylinders provided with the reduced air-fuel ratio than the remainder of the plurality of cylinders; and (e) determining a sensor malfunction based on a comparison of the first and second output signals. ### Claim 2 (depends on 1) The method according to claim 1, wherein determining a sensor malfunction comprises comparing a spectral composition of the first and second output signals. ### Claim 3 (depends on 1) The method according to claim 1, further comprising high-pass filtering the second output signal and determining the sensor malfunction when an amplitude of the high-pass filtered second output signal is less than a limit. ### Claim 4 (depends on 3) The method according to claim 3, further comprising determining the limit by multiplying an amplitude of the first output signal by a predetermined factor. ### Claim 5 (depends on 1) The method according to claim 1, further comprising determining an average value for a time derivative of the second output signal and determining the sensor malfunction when the average value drops below a limit. ### Claim 6 (depends on 5) The method according to claim 5, further comprising determining the limit by multiplying an amplitude of the first output signal by a predetermined factor. ### Claim 7 (depends on 1) The method according to claim 1, further comprising regulating the air-fuel ratio during (a) based on the first output signal. ### Claim 8 (depends on 1) The method according to claim 1, further comprising regulating the air-fuel ratio during (c) based on the second output signal. ### Claim 9 (depends on 8) The method according to claim 8, wherein during (c) a stoichiometric ratio is maintained on average over the plurality of cylinders. ### Claim 10 (depends on 9) The method according to claim 9, further comprising operating the second one of the plurality of cylinders at an air-fuel ratio that deviates in a range between 10% and 50% from the stoichiometric ratio. ### Claim 11 (depends on 1) The method according to claim 1, further comprising cyclically repeating (c) through (e). ### Claim 12 (depends on 11) The method according to claim 11, further comprising diminishing a difference between the air-fuel ratios of the cylinders when the sensor malfunction has been ruled out in (e) when cyclically repeating (c). ### Claim 13 (depends on 1) The method according to claim 1, further comprising issuing a warning when the sensor malfunction has been determined. ### Claim 14 (depends on 1) A non-transitory computer-readable data carrier comprising with program code having instruction that allow a computer to implement the method according claim 1. ### Claim 15 A device for detecting a malfunction of an oxygen sensor in an exhaust gas system of an internal combustion engine having a plurality of cylinders comprising an electronic control unit configured to: (a) operate the internal combustion engine such that each cylinder is provided with an equivalent air-fuel ratio; (b) monitor the oxygen sensor to obtain a first output signal during the operation of the internal combustion engine with each of the plurality of cylinders with the equivalent air-fuel ratio; (c) operate the internal combustion engine such that a first one of the plurality of cylinders is provided with an increase in air-fuel ratio by a value such that the first one of the plurality of cylinders has an air-fuel ratio that is greater than a remainder of the plurality of cylinders and a second one of the plurality of cylinders is provided with a decrease in air-fuel ratio by the value such that the second one of the plurality of cylinders is provided with an air-fuel ratio that is less than the remainder of the plurality of cylinders; (d) monitor the oxygen sensor to obtain a second output signal during the operation of the internal combustion engine with the first one of the plurality of cylinders with the increase in the air-fuel ratio and the second one of the plurality of cylinders with the decrease in the air-fuel ratio; (e) determine a sensor malfunction based on a comparison of the first and second output signals; based on a determination that the sensor is operating properly, decrease the value; repeat (a)-(e) and based on a determination that the sensor is malfunctioning, determine whether the value is greater than a minimum value; and based on a determination that the value is greater than the minimum value, output a warning.