Methods and systems are provided for a NO.sub.x sensor. In one example, a method includes heating a NO.sub.x sensor during a vehicle off in response to a cumulative heat energy applied to the NO.sub.x.

With respect to a vehicle mass air-flow sensor that includes a temperature sensor for measuring a temperature of a sensor element of the mass air-flow sensor, a method for controlling a heating element for heating the sensor element of a mass air-flow sensor includes identifying a dew formation on the sensor element by evaluating a temperature profile that is recorded during an operation of the vehicle using the temperature sensor, and generating a switch-on signal for switching on the heating element in response to the identification of the dew formation.

A gas sensor is provided in an exhaust passage of an engine mounted on a vehicle. The gas sensor includes a sensor element and a heater. The sensor element detects a concentration of a specific component in exhaust gas. The heater is energized with electricity from a power source to heat the sensor element. The heater energization control device controls an amount of electricity supplied to the heater. An ambient temperature acquisition unit acquires an ambient temperature, which is a temperature of an environment surrounding the engine. An energization control unit controls the amount of electricity supplied to the heater based on the ambient temperature in temperature raising energization in which a temperature of the sensor element is raised to an active temperature when the engine is started.

Methods and systems are provided for adapting a target impedance of an oxygen sensor. In one example, a method may include updating a target impedance of an oxygen sensor based on a difference between an estimated voltage across a sensing element of the oxygen sensor and a reference RMS voltage of the sensing element. The temperature of the oxygen sensor may be adjusted based on the updated target impedance.

A method for operating a sensor for detecting particles in a measuring gas. The sensor includes a sensor element having an electrically insulating element substrate, a first electrode, and a second electrode. The first electrode and the second electrode is situated at the electrically insulating element. The first electrode and the second electrode carry out a current and/or voltage measurement. The sensor is operated in at least one measuring phase during which a first voltage is applied to the first electrode and the second electrode. A second voltage is applied to the first and second electrode during a predetermined time period outside the measuring phase, the second voltage being lower than a decomposition voltage for water. The presence of water on the sensor element is inferred if the current and/or voltage measurement, with the second voltage being applied, yields a value which exceeds a threshold value for an electric current.

Failure detection apparatus for a particulate filter includes: a sensor having a particulate matter detection unit that outputs a signal corresponding to the amount of accumulated PM, and a heater unit that heats the particulate matter detection unit; a regeneration control unit that causes the heater unit to heat the particulate matter detection unit to a regeneration temperature allowing the particulate matter to be burned off; a start detection unit that determines the start of the internal combustion engine; failure determination unit that determines whether exhaust gas contains water droplets while the engine is in operation; a heating control unit that causes the heater unit to heat the particulate matter detection unit to a first temperature allowing the accumulated particulate matter to remain and the moisture included in the particulate matter to be removed; and failure determination unit that determines whether the filter has failure based on a sensor output value.

A particulate matter (PM) sensor circuit arrangement includes a PM sensor. The sensor includes, integral therewith, a PM sensor resistor, a resistive temperature device (RTD) resistor, and a heater resistor. The PM sensor includes four terminal pins, of which a) a first terminal pin is connected to one terminal of the PM sensor resistor; a second terminal pin is connected to one terminal side of said RTD resistor; c) a third terminal pin being connected to one terminal of a heater resistor; and d) a fourth common terminal pin is connected to respective opposite terminals of the PM sensor resistor, RTD resistor, and heater resistor to the first, second, and third terminal pins. The fourth common terminal pin is operationally connected to a boost or voltage supply and the first pin is connected to a low side line.

A hybrid vehicle may include an engine controller that determines an activation state of an oxygen sensor when the engine controller is requested to operate an engine and controls a voltage applied to the oxygen sensor depending on whether or not the oxygen sensor is in an activated state, and a vehicle controller that controls a voltage of a battery of the hybrid vehicle and applies the voltage of the battery to the engine controller. The engine controller outputs an activation demand signal for the oxygen sensor to be activated to the vehicle controller when it is determined that the oxygen sensor is not in the activated state.

An air-fuel ratio control system (1) including an air-fuel ratio control section (3) for controlling the air-fuel ratio λ of an air-fuel mixture, an exhaust gas purifier (4); an air-fuel ratio sensor (5) whose output changes sharply when λ in the exhaust gas changes between rich and lean sides about a stoichiometric air-fuel ratio; a heater (6); and a temperature control section (7). The air-fuel ratio control section (3) controls λ based on the output of the air-fuel ratio sensor (5) using, as a target air-fuel ratio, a predetermined air-fuel ratio such that 0.980≤λ<1.000 is satisfied, and when a change amount Δλ λ is 0.008, an output difference ΔV is 150 mV or smaller. The temperature control section (7) controls the temperature of the air-fuel ratio sensor (5) to a predetermined target temperature of 650° C. or higher.

An EHC line leakage diagnosis method can operate a heater of an oxygen detector when satisfying one or more conditions of an engine off time, a coolant temperature, and an outside air temperature by a diagnosis controller upon the key-on of the non-operation of an engine, and then, determine the normality or abnormality of a temperature drop using a change in a temperature value of a signal value and the temperature value detected by the oxygen detector after an air pump is driven, and then confirm the leakage of an exhaust line and a line on the rear end portion of an EHC valve of an air line using the number of times of the occurrence of the abnormality of the temperature drop, and can perform the failure diagnosis without generating the exhaust gas by not operating an engine.