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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 recirc

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.

대표청구항 ▼

1. A method of operating an engine including a humidity sensor, comprising, indicating humidity sensor degradation based on each of a change in an intake air relative humidity and temperature over a duration since an engine cold-start, the duration based on an exhaust catalyst temperature. 2. The me

1. A method of operating an engine including a humidity sensor, comprising, indicating humidity sensor degradation based on each of a change in an intake air relative humidity and temperature over a duration since an engine cold-start, the duration based on an exhaust catalyst temperature. 2. The method of claim 1, wherein the relative humidity is estimated by the humidity sensor, and wherein the temperature is estimated by a temperature sensor, each of the humidity sensor and the temperature sensor positioned in an engine intake, downstream of a first throttle valve. 3. The method of claim 1, wherein the indication includes indicating humidity sensor degradation responsive to a ratio of the change in humidity to the change in temperature, over the duration, being lower than a threshold. 4. The method of claim 1, wherein the indication includes indicating humidity sensor degradation responsive to a difference between the change in humidity and the change in temperature, over the duration, being higher than a threshold. 5. The method of claim 1, wherein the indication includes setting a diagnostic code. 6. The method of claim 1, wherein the duration is increased as a difference between the exhaust catalyst temperature and a threshold temperature increases. 7. The method of claim 1, wherein the engine includes an engine intake, an engine exhaust, an EGR loop coupled between the engine intake and the engine exhaust, and wherein an EGR flow through the EGR loop is adjusted based on the indication of degradation. 8. The method of claim 1, wherein the adjustment includes, adjusting the EGR flow based on an output of the humidity sensor when the humidity sensor is not degraded, and adjusting the EGR flow based on a maximum humidity assumption when the humidity sensor is degraded. 9. A method of operating a turbocharged engine including a humidity sensor and a temperature sensor in an engine intake, comprising, during an engine cold-start condition,estimating each of an intake air temperature and relative humidity over a duration since the cold-start;indicating humidity sensor degradation based on a change in the humidity relative to a change in the temperature over the duration; andadjusting an amount of exhaust gas recirculated from an engine exhaust to the engine intake based on the indication of humidity sensor degradation, the relative humidity indicative of likelihood of condensation at a turbocharger compressor, the adjusting including adjusting the amount to reduce condensation assuming a maximum relative humidity. 10. The method of claim 9, wherein the indication includes indicating degradation if a ratio of the change in humidity to the change in temperature is lower than a threshold and/or if a difference in the change in humidity to the change in pressure is higher than a threshold. 11. The method of claim 9, wherein the duration is based on an exhaust catalyst temperature, the duration increased as a difference between the exhaust catalyst temperature and a threshold temperature increases. 12. The method of claim 10, wherein the engine cold-start condition includes the exhaust catalyst temperature being below a light-off temperature. 13. The method of claim 11, wherein exhaust gas is recirculated from the engine exhaust to the engine intake via an EGR loop including an EGR valve, and wherein adjusting the amount of exhaust gas recirculated includes adjusting a position of the EGR valve. 14. The method of claim 13, wherein the adjustment includes, adjusting the position of the EGR valve based on an output of the humidity sensor if the humidity sensor is not degraded; andadjusting the position of the EGR valve based on the maximum humidity if the humidity sensor is degraded, the maximum humidity calculated based on engine operating conditions. 15. An engine system, comprising: first and second parallel intake passages, each including a turbocharger compressor upstream of engine cylinders, the cylinders including a direct fuel injector;first and second parallel exhaust passages, each including a turbocharger turbine;a humidity sensor and a temperature sensor, each positioned only in the first passage; anda controller configured with instructions for indicating humidity sensor degradation responsive to a humidity change relative to a temperature change over a duration since an engine cold-start. 16. The system of claim 15, further comprising, a first low-pressure EGR loop for recirculating at least some exhaust gas from the first parallel exhaust passage, downstream of the turbine, to the first parallel intake passage, upstream of the compressor;a second low-pressure EGR loop for recirculating at least some exhaust gas from the second parallel exhaust passage, downstream of the turbine, to the second parallel intake passage, upstream of the compressor;a first high-pressure EGR loop for recirculating at least some exhaust gas from the first parallel exhaust passage, upstream of the turbine, to the first parallel intake passage, downstream of the compressor; anda second high-pressure EGR loop for recirculating at least some exhaust gas from the second parallel exhaust passage, upstream of the turbine, to the second parallel intake passage, downstream of the compressor. 17. The system of claim 16, wherein the indication includes indicating sensor degradation responsive to the humidity change estimated by the humidity sensor being disproportionate to the temperature change estimated by the temperature sensor over the duration since the engine cold-start. 18. The system of claim 17, wherein the controller is further configured to, recirculate a first amount of exhaust gas through the first and second low-pressure EGR loops in response to an indication of no humidity sensor degradation, the first amount based on a humidity output of the humidity sensor; andrecirculate a second, different amount of exhaust gas through the first and second low-pressure EGR loops in response to the indication of humidity sensor degradation, thesecond amount based on a maximum humidity assumption. 19. The system of claim 17, further comprising an exhaust catalyst, wherein the duration is based on a temperature of the exhaust catalyst, the duration increased as a difference between the temperature of the exhaust catalyst and a threshold temperature increases.