A controller is used for an air-fuel ratio sensor. The air-fuel sensor includes a detection element that detects an oxygen concentration, and a PWM-controlled heater that receives a PWM signal for temperature control of the detection element. The controller includes a resistance detection circuit configured to detect a resistance of the detection element, and a processor. The processor is programmed to generate the PWM signal for the heater based on the detected resistance such that the resistance of the detection element is kept at a predetermined target resistance, and determine whether a failure has occurred in the air-fuel ratio sensor based on a manner of time-series increase in duty cycle of the PWM signal.

The present disclosure provides a method for predicting a fluid type, comprising sensing, by a first sensor, mass flow data of a fluid in an engine, wherein the first sensor operates based on a first fluid property; sensing, by a second sensor, mass flow data of the fluid, wherein the second sensor operates based on a second fluid property; and detecting, by a logic circuit of a controller, a percent difference in the mass flow data provided by the first and second sensors, the percent difference indicating that the fluid is comprised of at least a first fluid type.

Methods and systems are provided sensing particulate matter by a particulate matter (PM) sensor positioned downstream of a diesel particulate filter (DPF) in an exhaust system, where the PM sensor may include plurality of individual electrode pairs coupled to plurality of voltage sources and further to plurality of measurement devices. In one example, a method may include determining a total PM sensor current by summing current generated across the plurality of electrode pairs by determining the sum total of the current generated across the individual electrode pairs. In this way, the PM sensor may detect PMs in the exhaust more accurately, and not be affected by large particulates depositing on the electrodes.

A constant current circuit is controlled to stop a constant current Ics (Ics=0) flowing between sensor electrodes of an oxygen sensor, in a period before the oxygen sensor becomes active, during a fuel cut of an engine, and after the engine stops. When an abnormality (for example, a failure) occurs in the constant current circuit, a sensor output equivalent to an output of the oxygen sensor of when the constant current circuit is controlled to stop the constant current Ics is different from a normal sensor output. An abnormality diagnosis is executed to determine a presence or absence of the abnormality in the constant current circuit depending on whether the output of the oxygen sensor is out of a predetermined normal range, in a period before the oxygen sensor becomes active, during a fuel cut of an engine, and after the engine stops (when the constant current circuit is controlled to stop the constant current Ics).

The invention relates to a method and to a regulating device for regulating an air-fuel ratio of an internal combustion engine (10), wherein an exhaust-gas composition of an exhaust gas of the internal combustion engine (10) is determined by virtue of an actual probe signal, which is dependent on the exhaust-gas composition, being detected by means of an exhaust-gas probe (22) and the exhaust-gas composition being determined as a function of the actual probe signal by means of a characteristic curve or a calculation rule, and wherein the determined exhaust-gas composition is compared with a setpoint value or a threshold value, the attainment or exceedance of which triggers a manipulation of the air-fuel ratio supplied to the internal combustion engine (10), wherein, in order to take into consideration at least one disturbance variable which affects the actual probe signal, a safety margin (S) is defined which is applied to the characteristic curve or calculation rule, to the actual probe signal or to the setpoint value or threshold value. It is provided that an evaluation of a present accuracy of the at least one disturbance variable and/or of a present influence of the at least one disturbance variable on the probe signal is performed, and the safety margin (S) owing to the at least one disturbance variable is defined as a function of the evaluation.

An object of the present invention is to reliably detect clogging in a cover even during a period corresponding to a dead zone of a detection apparatus. A PM sensor includes an element section, an element temperature detection section, a heater, and an element cover. An ECU detects clogging in the element cover based on a difference between an element temperature and an exhaust temperature when the exhaust temperature rises. Furthermore, the ECU detects clogging in the element cover based on temperature rising characteristics of the element section observed when the element section is heated by the heater. Thus, even during the period corresponding to the dead zone of the PM sensor, clogging in the element cover can be reliably detected, thus improving the reliability of the sensor.

Methods and systems are provided sensing particulate matter by a particulate matter (PM) sensor positioned downstream of a diesel particulate filter (DPF) in an exhaust system, where the PM sensor may include plurality of individual electrode pairs coupled to plurality of voltage sources and further to plurality of measurement devices. In one example, a method may include determining a total PM sensor current by summing current generated across the plurality of electrode pairs by determining the sum total of the current generated across the individual electrode pairs. In this way, the PM sensor may detect PMs in the exhaust more accurately, and not be affected by large particulates depositing on the electrodes.