A system (70) for actively controlling sound propagating through exhaust systems (40) includes a controller (90), a sound generator (30), in fluid communication with an exhaust system (40), and an actuator (20), inside the sound generator and receiving a controller control signal for generating sound inside the sound generator to reduce sound inside the exhaust system. The controller identifies an increased exhaust pressure inside the exhaust system based on signals output by an error microphone (50), a temperature sensor (51), an impedance measuring bridge (52), a bus system (53), or a water sensor (54). The controller interrupts a generation of the control signal and/or interrupts an output of the control signal to the at least one actuator and/or reduces a level of the control signal output to the at least one actuator by at least 30% or at least 60% upon determining a presence of an excessive exhaust gas pressure.

Methods and systems are provided for operating an exhaust oxygen sensor coupled to an exhaust passage of an internal combustion engine in response to detecting water at the sensor. In one example, a method may include indicating water at an exhaust oxygen sensor positioned in an engine exhaust passage based on a sensor parameter of the exhaust oxygen sensor while operating the exhaust oxygen sensor in a variable voltage (VVs) mode where a reference voltage is adjusted from a lower, first voltage to a higher, second voltage; and adjusting one or more of sensor operation and engine operation based on the indicating water.

Methods and systems are provided for diagnosing a humidity sensor positioned in an intake system of a vehicle engine system. In one example, a method comprises rotating an engine unfueled in reverse and injecting a fluid into an exhaust system of the engine system, to draw the fluid into the intake system, where a humidity sensor output signal greater than a baseline output signal by a predetermined threshold is indicative of a humidity sensor that is functioning as desired. In this way, a humidity sensor may be periodically rationalized which may prolong engine lifetime by ensuring the engine is operating at optimal parameters.

Methods and systems are provided for diagnosing a humidity sensor positioned in an intake system of a vehicle engine system. In one example, a method comprises rotating an engine unfueled in reverse and injecting a fluid into an exhaust system of the engine system, to draw the fluid into the intake system, where a humidity sensor output signal greater than a baseline output signal by a predetermined threshold is indicative of a humidity sensor that is functioning as desired. In this way, a humidity sensor may be periodically rationalized which may prolong engine lifetime by ensuring the engine is operating at optimal parameters.

A method of recovering catalyst performance includes providing a vanadium selective catalytic reduction (VSCR) catalyst. The method includes exposing the VSCR catalyst to a first humidity level in a range of 50%-100% relative humidity, at a first temperature in a range of 20? C.-100? C., for a first period of time of at least two hours. The method includes thermally treating the VSCR catalyst at a second temperature in a range of 300? C.-600? C. for a second period of time of at least than one hour.

Methods for monitoring thermal characteristics of oxidation catalyst (OC) catalytic composition(s) (CC) are provided, and comprise communicating exhaust gas to the OC, and determining a temperature change of the CC for the time frame based on a plurality of heat sources including heat imparted to the CC from exhaust gas enthalpy, heat imparted to the CC via oxidation of HC and/or CO in exhaust gas, heat imparted to the CC via water present in the exhaust gas condensing on the CC or heat removed from the CC via water evaporating from the CC, and optionally heat exchanged between the CC and the ambient environment. Heat imparted to the CC via water condensing on the CC can be determined using an increasing relative humidity proximate the CC, and heat removed from the CC via water evaporating from the CC can be determined using a decreasing relative humidity proximate the CC.

Methods and systems are provided for controlling exhaust catalyst temperature during an engine cold-start by water injection. In one example, a method may include during the engine cold-start, injecting water into an intake of an engine based on the exhaust catalyst temperature and accumulating water molecules within an exhaust catalyst to generate heat within the exhaust catalyst. In this way, by generating and storing heat within the exhaust catalyst, the exhaust catalyst may be heated up rapidly, thus reducing catalyst light-off time.

The invention is directed to a method for determining the state of aging of a catalytic converter (2). The disclosed method functions in a non-contacting manner as resonances formed when the catalytic converter (2) located in a housing is excited with high-frequency electromagnetic waves are analyzed.

A device and method for correcting emissions can include a first sensor that measures a sample of air not containing an exhaust gas, and a second sensor, wherein the exhaust gas enters a settling chamber and a relative humidity of the exhaust gas is measured by the second sensor. A microcomputer can calculate a mass of water vapor in the sample of air measured by the first sensor and in the exhaust gas measured by the second sensor and can determine a dilution factor of the measured exhaust gas. The dilution factor can be used for correcting emissions based on the measurements of the exhaust gas made by the first sensor and the second sensor. The first and second sensors can comprise one or more of, for example, a relative humidity sensor, a dew point sensor, a trace water vapor sensor and/or other types of sensors.

An emission control system, such as an emission control system for a diesel engine, which includes both a NOx sensor and an electrostatic Particulate Matter (ePM) sensor, and uses the signal from the ePM sensor to determine when it is safe to activate and heat up the NOx sensor after engine ignition. This is performed as soon as moisture clears the exhaust, without having to wait any additional time as a safety factor to maximize the reliability of the NOx sensor against damage from water thermal shock. It also allows for a higher degree of application flexibility for a specific engine and aftertreatment combination to be used in a variety of vehicle applications, environmental conditions, and vehicle operating profiles.