An air-fuel ratio controller of an internal combustion engine includes an open-loop processor setting a base injection amount, a feedback processor calculating a feedback operation amount, an increase processor performing an increase correction on the base injection amount when a temperature of the internal combustion engine is a specified temperature or lower, an operation processor operating a fuel injection valve based on the corrected base injection amount and that is corrected using the feedback operation amount and a learning value, and an update processor updating the learning value. If the increase processor performs the increase correction, the update processor updates the learning value to increase an increase correction rate of the base injection amount when a temperature of the cylinder wall surface is high.

In a method and device for controlling and/or monitoring the function of a secondary air supply in an emission control system of an internal combustion engine, the emission control system includes at least two catalytic converters situated in succession in an exhaust duct, it being possible for the second catalytic converter to be implemented as a combination of catalytic converter and particulate filter. For a secondary air diagnosis and for secondary air control, a two-point lambda probe is situated, with respect to a direction of flow of exhaust gas, downstream of the first catalytic converter. Measures are applied for compensating tolerance and aging effects of the two-point lambda probe. This results in particular in cost advantages in emission control systems for fulfilling stricter emission requirements. In particular, this makes it possible to operate the particulate filter in optimized fashion.

A method and control device for correcting an output signal of an exhaust gas sensor in an exhaust gas conduit of an internal combustion engine, a secondary air delivery system for delivering air into the exhaust gas conduit being associated with the exhaust gas conduit upstream from the exhaust gas sensor in the flow direction of the exhaust gas. During a measurement of the output signal of the exhaust gas sensor, air is delivered to the exhaust gas conduit via the secondary air delivery system during a correction phase by way of which a correction of the output signal of the exhaust gas sensor is derived. In this operating mode, a defined oxygen content exists in the gas mixture surrounding said sensor, so that the output signal can be compared with reference values.

An exhaust aftertreatment system including a selective catalytic reduction device (SCR), a NOx sensor and a reductant injection system is described. A method for controlling the reductant injection system to inject reductant into the exhaust gas feedstream upstream relative to the SCR includes monitoring engine operation, and determining an initial reductant dosing rate responsive to the engine operation. A dosing perturbation is induced in the reductant dosing rate. The exhaust gas feedstream is monitored via the NOx sensor, and a reductant dosing correction term is determined based upon the monitoring. A final dosing rate for controlling the reductant injection system is determined based upon the initial reductant dosing rate, the dosing perturbation, and the reductant dosing correction term

A control and evaluation unit for the operation and evaluation of at least one sensor, in particular for the operation and evaluation of at least one lambda probe of an internal combustion engine, signal inputs being disposed for the reception of analog measured signals of the at least one sensor, received analog measured signals being digitized by way of an analog/digital converter, a signal transfer unit, by way of which digitized signals are transferred to a calculation unit, being disposed, and provision being made in particular that the signal inputs are switchable by way of a multiplexer.

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.

A diagnostic method is provided for testing a gas sensor mounted in an exhaust gas stream of an internal combustion engine provided with an after treatment system and a diagnostic motor management module. The method comprises receiving a gas sensor signal from the gas sensor as subsequent gas sensor sample values in a time window; detecting a noise component from the gas sensor signal; deriving a sensor baseline condition in the diagnostic motor management module in case of a noise component detected at a value higher than a preset noise threshold value, and deriving a fault sensor condition in the diagnostic motor management module in case of a noise component detected at a value lower than the preset noise threshold value.

An O.sub.2 sensor has a sensor element, which includes a solid electrolyte layer and a pair of electrodes, while the solid electrolyte layer is interposed between the electrodes. The O.sub.2 sensor outputs an electromotive force signal in response to an air-to-fuel ratio of exhaust gas of an engine, which serves as a sensing subject. A constant current circuit, which induces a flow of a predetermined constant electric current between the pair of electrodes of a sensor element, and a current sensing arrangement, which senses a current value of an actual electric current that is conducted through the sensor element, are provided. A microcomputer determines whether an abnormality of the constant current circuit is present based on the current value of the electric current, which is sensed with the current sensing arrangement, in a case where the constant current is induced by the constant current circuit.

A sensor for detecting electrically conductive and/or polarizable particles, in particular for detecting soot particles, includes a substrate and at least two electrode layers, a first electrode layer and at least one second electrode layer, which is arranged between the substrate and the first electrode layer. At least one insulation layer is formed between the first electrode layer and the at least one second electrode layer and at least one opening is formed in both the first electrode layer and the at least one insulation layer. At least some sections of the opening in the first electrode layer and of the opening in the insulation layer are arranged one above the other, such that at least one passage is formed to the second electrode layer.

A control device of an exhaust sensor comprises a cell temperature detecting part detecting a temperature of the electrochemical cell, a heater control part controlling the heater so that a temperature of the electrochemical cell becomes the target temperature, and a judging part judging whether a water repellency of the protective layer is falling. The judging part judges that the water repellency of the protective layer is falling if a condition for judging abnormality is satisfied. The condition for judging abnormality includes a temperature of the electrochemical cell detected by the cell temperature detecting part falling from the target temperature and a speed of fall of the temperature being faster than a speed of fall of the temperature of the electrochemical cell when the heater is turned off.