Method and system for humidity sensor diagnostics
First Claim
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1. An engine method, comprising:
- closing a first throttle valve arranged in an engine intake passage upstream of an outlet of an EGR passage into the intake passage;
determining whether a relative humidity change estimated by a humidity sensor downstream of the first throttle valve responsive to the first throttle valve closing is proportional to a pressure change estimated by a pressure sensor downstream of the first throttle valve responsive to the first throttle valve closing, and if it is not, indicating degradation of the humidity sensor.
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Abstract
Methods and systems are provided for an engine including a humidity sensor. Degradation of the humidity sensor may be determined based on a change in intake air relative humidity as compared to a change in intake air temperature or pressure, under selected conditions. An amount of exhaust gas recirculated to an engine intake is adjusted differently based on whether the humidity sensor is degraded or functional.
58 Citations
20 Claims
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1. An engine method, comprising:
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closing a first throttle valve arranged in an engine intake passage upstream of an outlet of an EGR passage into the intake passage; determining whether a relative humidity change estimated by a humidity sensor downstream of the first throttle valve responsive to the first throttle valve closing is proportional to a pressure change estimated by a pressure sensor downstream of the first throttle valve responsive to the first throttle valve closing, and if it is not, indicating degradation of the humidity sensor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of operating an engine including a humidity sensor in an engine intake, comprising:
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closing a first throttle valve while concurrently opening a second throttle valve, the first throttle valve positioned in an engine intake passage upstream of the humidity sensor and upstream of an outlet of an EGR passage into the intake passage, the second throttle valve positioned downstream of the humidity sensor; determining whether the humidity sensor is degraded based on a change in relative humidity estimated by the humidity sensor responsive to the first throttle valve closing and a change in pressure estimated by a pressure sensor arranged downstream of the first throttle valve responsive to the first throttle valve closing; and adjusting an amount of exhaust gas recirculated from an engine exhaust to the engine intake, the adjustment based on whether the humidity sensor is degraded. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A method of operating an engine including a humidity sensor arranged in an engine intake, comprising:
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closing a first throttle valve positioned in an engine intake passage upstream of the humidity sensor and upstream of an outlet of an EGR passage into the intake passage while concurrently opening a second throttle valve positioned downstream of the humidity sensor; comparing a change in relative humidity estimated by the humidity sensor responsive to the first throttle valve closing with a change in pressure estimated by a pressure sensor arranged downstream of the first throttle valve responsive to the first throttle valve closing; determining whether the humidity sensor is functional or degraded based on the comparison; and adjusting an amount of low-pressure exhaust gas recirculated from an engine exhaust to the engine intake differently based on whether the humidity sensor is functional or degraded. - View Dependent Claims (17, 18, 19, 20)
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Specification