Abstract: Methods and systems are provided for diagnosing an intake oxygen sensor. In one example, a method may include indicating degradation of an intake oxygen sensor based on a first time constant of an output of the intake oxygen sensor and a second time constant of an output of a throttle inlet pressure sensor. The method may further include adjusting EGR flow based on the output of the intake oxygen sensor and the output of the throttle inlet pressure sensor when the intake oxygen sensor is not degraded.

Abstract: Methods and systems are provided for estimating exhaust gas recirculation (EGR) flow based on outputs of two different intake oxygen sensors arranged in an engine intake system. In one example, a method may include, when the engine is boosted, adjusting exhaust gas recirculation (EGR) based on a first output of a first oxygen sensor positioned in an intake passage and exposed to EGR gases and a second output of a second oxygen sensor not exposed to EGR gases and exposed to positive crankcase ventilation and purge flow gases. For example, EGR flow may be estimated based on a difference between the first output and the second output.

Abstract: Embodiments for diagnosing a humidity sensor are provided. One example method comprises adjusting an engine operating parameter based on humidity of a first gas flow measured by a humidity sensor, and indicating degradation of the humidity sensor if a humidity of a second gas flow measured by the humidity sensor is different than an expected humidity. In this way, degradation of the humidity sensor may be indicated if the humidity of the second gas flow measured by the humidity sensor is different than expected.

Abstract: Methods and systems are provided for determining an amount of alcohol in fuel injected into an engine based on outputs from an exhaust gas sensor. In one example, a method includes estimating a first fuel alcohol content based on an air-fuel ratio estimated with the exhaust oxygen sensor and estimating a second fuel alcohol content based on a change in sensor output during modulating a reference voltage of the exhaust oxygen sensor between a first and second voltage. The method further includes adjusting engine operation based on a difference between the first and second fuel alcohol contents.

Abstract: Methods and systems are provided for diagnosing an intake oxygen sensor. In one example, a method may include indicating degradation of an intake oxygen sensor based on a first time constant of an output of the intake oxygen sensor and a second time constant of an output of a throttle inlet pressure sensor. The method may further include adjusting EGR flow based on the output of the intake oxygen sensor and the output of the throttle inlet pressure sensor when the intake oxygen sensor is not degraded.

Abstract: Methods and systems are provided for correcting an EGR rate determined based on an intake manifold oxygen sensor based on an air-fuel ratio of EGR. The output of the sensor is corrected to compensate for extra fuel in rich EGR or extra air in lean EGR and used to reliably estimate the EGR rate. One or more engine operating parameters are adjusted based on an uncorrected output of the sensor.

Abstract: Embodiments for diagnosing a humidity sensor are provided. One example method comprises adjusting an engine operating parameter based on humidity of a first gas flow measured by a humidity sensor, and indicating degradation of the humidity sensor if a humidity of a second gas flow measured by the humidity sensor is different than an expected humidity. In this way, degradation of the humidity sensor may be indicated if the humidity of the second gas flow measured by the humidity sensor is different than expected.

Abstract: Embodiments for testing a humidity sensor are provided. One example method comprises indicating degradation of a humidity sensor based on a humidity sensor output and output from an intake gas composition sensor. In this way, output from the intake gas composition sensor may be used to determine if the humidity sensor is degraded.

Abstract: Methods and systems for operating an engine during conditions where ambient humidity changes over time are presented. In one non-limiting example, an engine airflow is adjusted to increase engine airflow during high humidity conditions such that an engine may provide equivalent torque output during the high humidity conditions as compared to when the engine is operated during low humidity conditions.

Abstract: Methods and systems are provided for accurately learning the zero point of an intake gas oxygen sensor during selected engine no-fueling conditions. The learned zero point is used to infer EGR flow and accordingly adjust EGR valve control. In addition, EGR valve leakage is diagnosed based on the zero point learned during a DFSO adaptation relative to a zero point learned during an idle adaptation.

Abstract: Methods and systems are provided for determining an amount of alcohol in fuel injected into an engine based on outputs from an exhaust gas sensor. In one example, a method includes estimating a first fuel alcohol content based on an air-fuel ratio estimated with the exhaust oxygen sensor and estimating a second fuel alcohol content based on a change in sensor output during modulating a reference voltage of the exhaust oxygen sensor between a first and second voltage. The method further includes adjusting engine operation based on a difference between the first and second fuel alcohol contents.

Abstract: A diagnostic method for a capacitive humidity sensor comprising a heater, and a capacitance-sensing element that individually identifies heater, temperature-sensing element, or capacitance-sensing element degradation. By this method, individual elements of the sensor may be replaced or compensated for to allow for further operation.

Abstract: Methods and systems are provided for determining changes in a flow area of an exhaust gas recirculation (EGR) valve for EGR flow estimates due to soot accumulation on the EGR valve. In one example, a method includes indicating soot accumulation on the EGR valve based on a difference in EGR flow estimated with an intake oxygen sensor and with a pressure sensor coupled across the EGR valve. The determination of the difference of the EGR flow estimates may occur when the engine is not boosted.

Abstract: Various methods and system are described for determining ambient humidity via an exhaust gas sensor disposed in an exhaust system of an engine. In one example, a reference voltage of the sensor is modulated between a first and second voltage during non-fueling conditions of the engine. The ambient humidity is determined based on an average change in pumping current while the voltage is modulated.

Abstract: Methods and systems are provided for indicating water at an oxygen sensor based on power consumption of a heating element of the oxygen sensor. In one example, water may be indicated at an oxygen sensor positioned in an intake of an engine responsive to power consumption of the heating element of the oxygen sensor increasing above a baseline level. Engine operating parameters may then be adjusted based on the water indication and the power consumption.

Abstract: Methods and systems are provided for an engine coupled capacitance-based humidity sensor. Degradation of the humidity sensor may be determined based on humidity readings while flowing gasses into an engine intake air downstream of the humidity sensor and upstream of a compressor change by less than a first threshold while pressure at the sensor changes greater then a second threshold. The variation in pressure can be changed by adjusting a throttle upstream and downstream of the compressor based on whether the humidity sensor is degraded or functional.

Abstract: Embodiments for testing a humidity sensor are provided. One example method comprises indicating degradation of a humidity sensor based on a humidity sensor output and output from an intake gas composition sensor. In this way, output from the intake gas composition sensor may be used to determine if the humidity sensor is degraded.

Abstract: Methods and systems are provided for accurately learning the zero point of an intake gas oxygen sensor in varying ambient humidity conditions. The learned zero point is corrected based on an estimated ambient humidity to calibrate the reading for dry air conditions or standard humidity conditions. EGR control is performed by comparing the output of an intake oxygen sensor during EGR conditions relative to the humidity-corrected zero point.

Abstract: Various systems and methods are described for an engine system with an exhaust gas recirculation system. In one example method, a correction for a gas constituent sensor is determined based on output from the gas constituent sensor and output from a pressure sensor over a range of boost pressure. The gas constituent sensor output is adjusted based on the correction, and an amount of exhaust gas recirculation is adjusted based on the adjusted gas constituent sensor output.

Abstract: Methods and systems are provided for diagnosing an intake oxygen sensor. In one example, a method may include indicating degradation of an intake oxygen sensor based on a first time constant of an output of the intake oxygen sensor and a second time constant of an output of a throttle inlet pressure sensor. The method may further include adjusting EGR flow based on the output of the intake oxygen sensor and the output of the throttle inlet pressure sensor when the intake oxygen sensor is not degraded.