Abstract: The ECU performs an on-board diagnosis for a NOx sensor. The diagnosis is carried out when an exhaust system of an engine is fully cooled after shut-down of the engine. The diagnosis is carried out after a temperature in the exhaust passage is lowered to an ambient temperature. In the diagnosis proceeding, the ECU activates a heater attached on the NOx sensor. The ECU detects a heating performance of the heater and determines whether the heating performance is sufficient or not. The NOx sensor is in a stable condition after the engine system is fully cooled. Therefore, it is possible to perform the diagnosis while eliminating or suppressing influences of operating conditions of the engine system and a residual heat in the exhaust system.

Abstract: A system for detecting when a gas concentration sensor has drifted or failed is disclosed. The system has a first gas concentration sensor configured to detect a first gas concentration and generate a corresponding first signal. The system also has a second gas concentration sensor configured to detect a second gas concentration and generate a corresponding second signal. In addition, the system has a controller in communication with the first and second gas concentration sensors. Based on the first and second signals, the controller is configured to provide an out-of-tolerance gas concentration sensor warning.

Abstract: An engine (12) has an exhaust system (16) containing a diesel particulate filter (DPF 20) and timer-based warning structure (30) for detecting and indicating particulate overloading of the DPF as the engine runs.

Abstract: An exhaust purification device includes a particulate filter (10), an air flow meter (7) that detects the amount of fresh air flowing in an intake passageway (3), and an EGR device (30) that supplies gas to a site in the intake passageway (3) between the air flow meter (7) and the particulate filter (10). The exhaust purification device detects the amount of flow of exhaust passing through the particulate filter on the basis of the amount of gas supplied by the EGR device (30), and the intake air amount detected by the air flow meter (S108), and detects the differential pressure between the upstream side and the downstream side of the particulate filter, and determines whether the particulate filter is clogged on the basis of the amount of flow and the differential pressure of exhaust (S110).

Abstract: A control system and method of monitoring a condition of a catalyst in a catalytic converter includes commanding a first air/fuel ratio. A first signal is monitored from a first oxygen sensor and a second signal from a second oxygen sensor. A second air/fuel ratio is commanded. A first time is determined based on the first oxygen sensor reaching a first threshold voltage. A second time is determined based on the second oxygen sensor reaching a second threshold voltage. A differential area defined by the first and second signals between the first and second times is calculated.

Abstract: A system, method, and software for triggering regeneration of an adsorber connected with a flow of exhaust from an engine. A sulfur loading estimate module is used to generate an estimated sulfur loading value associated with an adsorber. A desulfation trigger module is used to trigger a desulfation event for the adsorber upon detection of a trigger event comprising either a cost-effective trigger event, a loading trigger event, and a forced trigger event. A combustion manager module is used to control an engine through engine management to regenerate the adsorber during the desulfation event. A interrupt module is used to interrupt the desulfation event upon detection of an interrupt event. An end desulfation module is used to stop or end the desulfation event upon detection of an end desulfation event.

Abstract: Testing of temperature sensors (28, 30, 32) in an emission control system, such as in an exhaust system (10) of a diesel engine, serves to condition further component and/or system testing by determining that sufficient sensor cooling has occurred and that no sensor is “stuck within range” using a strategy (50).

Abstract: A method of operating a diesel engine in a mechanical apparatus is disclosed, wherein the diesel engine includes a combustion chamber, and wherein the mechanical apparatus also including a catalyst configured to treat NOx emissions from the diesel engine. The method includes performing at least one early homogenization combustion in the combustion chamber, determining a temperature of the catalyst, and if the temperature of the catalyst is equal to or below a preselected temperature threshold, then performing at least one late homogenization combustion or diffusion combustion in the combustion chamber to raise a temperature of exhaust provided to the catalyst.

Abstract: A nondestructive method for detecting internal defects of a filter, for example a catalytic filter, and a device for implementing the method. The method may be used in particular for treating a gas laden with soot particulates. The filter includes a honeycomb filter element or a plurality of honeycomb filter elements. In the method the presence or absence of the defects is determined by measuring a propagation of a gas stream such as air through the filter element or elements.

Abstract: An exhaust gas purifying apparatus for an internal combustion engine is provided.

Abstract: An oxygen concentration sensor including the sensor element for detecting oxygen concentration in the exhaust gas and the heater for heating the sensor element is installed at the location downstream of a DPF. An ECU controls power supply to the heater to make the sensor element at a predetermined active state. The ECU calculates heat data corresponding to a heat budget in the exhaust pipe in close proximity to the sensor location part after the engine startup, based upon an operating condition of the engine and a driving condition of a vehicle and also makes a determination as to dryness inside the exhaust pipe based upon the heat data. In addition, the power supply to the heater is controlled based upon the result of the dryness determination.

Abstract: An exhaust after-treatment system is disclosed. The system has a particulate trap disposed to remove particulate matter from an exhaust flow of an engine, an upstream temperature sensor disposed to measure a temperature of the exhaust flow upstream of the particulate trap, and a downstream temperature sensor disposed to measure a temperature of the exhaust flow downstream of the particulate trap. The system also has a controller in communication to receive from the upstream and downstream temperature sensors indications of the upstream and downstream temperatures. The controller is configured to compare the upstream and downstream temperatures, determine if the upstream and downstream temperature sensors are improperly swapped based on the comparison, and take a precaution if it is determined that the upstream and downstream temperature sensors are improperly swapped.

Abstract: A quantity of unburned fuel is provided through a combustion chamber of an engine and an exhaust conduit to a catalytic converter. The catalyst in the converter is determined to be non-operational if a post-catalyst temperature sensor does not indicate a sufficient temperature increase between readings before and after provision of the unburned fuel to the combustion chamber. The unburned fuel may be provided by withholding spark ignition to create a misfire in the combustion chamber or, particularly in a direct injection engine, by injecting the fuel during the exhaust stroke.

Abstract: An exhaust gas purifying system includes a catalyst arranged on an exhaust pipe of an internal combustion engine; a sensor detecting a state of the exhaust gas passed through the catalyst; and an ECU functioning as an abnormality determining apparatus determining abnormality by monitoring an output of said sensor in an operation under forced air-fuel ratio. When the operation under forced air-fuel control is interrupted before completion of the determination of system abnormality, the abnormality determining apparatus once stores a parameter accumulated during the operation under forced air-fuel ratio control by the time of interruption, and when the internal combustion engine comes to satisfy the prescribed condition again, resumes the operation under forced air-fuel ratio control, and completes determination of system abnormality using the stored parameter and the parameter accumulated after resumption of the forced air-fuel ratio control.

Abstract: A diagnostic apparatus for an internal combustion engine. An exhaust purification section includes an exhaust purifier disposed in an exhaust passage of the internal combustion engine, for purifying an exhaust emission, and a purifier activation section configured to control engine operating parameters of the internal combustion engine to promote activation of the exhaust purifier during the internal combustion engine being cold. The diagnostic apparatus is configured to determine a state of the exhaust purifier, to determine a total purifier out emission quantity as a quantity of the exhaust emission exiting the exhaust purifier during the internal combustion engine being cold, in accordance with the state of the exhaust purifier, and to determine normality of the exhaust purification section in accordance with the total purifier out emission quantity.

Abstract: An internal combustion engine includes an exhaust gas feedstream flowing past a gas sensing device disposed therein. The gas sensor includes an integrated electrical heating element which provides a resistance indicative of its temperature. An unknown input observer is used to determine the exhaust gas feedstream temperature based on the heating element temperature.

Abstract: In order to suppress deposition of constituent of a reducing agent (dissolved matter) in an exhaust passage of an engine enhancing an elimination rate of NOx even when temperature of an exhaust emission from the engine is low, an exhaust emission purifying apparatus is provided with an electro-generative-heat carrier provided on an upstream side of an injection nozzle that supplies the reducing agent into the exhaust emission on upstream side of a reduction catalyst in an exhaust pipe, the exhaust emission being heated to a temperature equal to or higher than a melting point of the dissolved matter whereby deposition of the dissolved matter on an inner wall surface of the exhaust pipe is suppressed to effectively use the supplied reducing agent for catalytic reduction reaction, even when the exhaust emission temperature is lower than the melting point of the dissolved matter of the reducing agent.

Abstract: A test method for an exhaust gas probe (8, 9) of an internal combustion engine (3), particularly for a lambda probe, has the following steps: Checking an output signal (?1, ?2) of the exhaust gas probe (8, 9), detecting a fault state of the exhaust gas probe (8, 9) on the basis of the output signal (?1, ?2) of the exhaust gas probe (8, 9) and differentiating between different fault states of the exhaust gas probe (8, 9).

Abstract: A system is provided for removing particulate matter from a diesel particulate filter. The diesel particulate filter includes at least one diesel particulate filter unit to filter particulate matter from diesel engine exhaust gas received from a diesel engine. The system includes a sensor positioned adjacent to at least one diesel particulate filter unit, where the sensor is configured to determine the extent of particulate matter trapped within the diesel particulate filter unit. The system further includes an engine controller coupled to the sensor and the diesel engine, where the sensor is configured to output a first alert signal to the engine controller upon determining that the trapped particulate matter exceeds a predetermined threshold. The engine controller is configured to increase the temperature of the diesel exhaust gas entering the diesel particulate filter upon receiving the first alert signal.

Abstract: A system is provided for removing particulate matter from a diesel particulate filter. The system includes an engine controller coupled to the diesel engine, and to a locomotive controller. The locomotive controller includes an algorithm to create a trip plan to optimize the performance of the locomotive along a route in accordance with a power setting of the diesel engine at each location along the route. Each sensor is configured to output a first alert signal to the engine controller once the trapped particulate matter exceeds a predetermined threshold. Upon receiving the first alert signal, the engine controller communicates with the locomotive controller to determine a time region or distance region within the trip plan when the power setting exceeds a power threshold. The engine controller increases the temperature of the diesel exhaust gas entering the diesel particulate filter during the time region or distance region.

Abstract: A clogging determination apparatus determines clogging of a DPF (Diesel Particulate Filter) such that exhaust pressure is estimated using a sensor deigned for regular control of an engine, without using exhaust pressure sensor. The apparatus includes: the DPF disposed in an exhaust system; an exhaust sensor that measures an air-fuel ratio ? in exhaust gas; and an injector that changes the air-fuel ratio in an cylinder through post-injection. A response time T taken for the exhaust sensor to detect a change in the air-fuel ratio is measured from the time when the post-injection is output from the injector. If this response time T is longer than a clogging determination response time To, the apparatus determines that the DPF is clogged.

Abstract: An apparatus, system, and method are disclosed for determining the reliability of an estimate such as particulate accumulation on a diesel particulate filter, weighing the estimate according to a function of its reliability, weighing a prediction of particulate accumulation on the filter according to a function of the estimate's reliability, and combining the weighted estimate and weighted prediction to determine a combined particulate load estimate. The degree of reliability can be expressed as a trust factor, and a function of the trust factor can be used in a low-pass filter of the estimate. The trust factor value depends on filter air flow and particulate distribution in one embodiment. Regeneration of the particulate filter may be initiated depending on the value of the combined particulate load estimate.

Abstract: An air-fuel ratio control system includes: a catalyst; an oxygen concentration sensor; an integral value calculation portion that calculates an integral value of a deviation updated by integrating the deviation between an output value from the oxygen concentration sensor and a reference value; an air-fuel ratio control portion that controls an air-fuel ratio of exhaust gas entering the catalyst to be equal to a target air-fuel ratio; a target air-fuel ratio switching portion that sets a rich target air-fuel ratio when the output value has been inverted from rich to lean while sets a lean target air-fuel ratio when the output value has been inverted from lean to rich; and an integral value correction portion that corrects the integral value of the deviation when the air-fuel ratio is being controlled to a switched target air-fuel ratio, based on whether the next inversion takes place within a predetermined time period from the last inversion.

Abstract: An apparatus, system, and method are disclosed for determining a time-temperature history of an aftertreatment device. The apparatus includes an aftertreatment device comprising a substrate, and at least one thermal monitoring member (TMM) in thermal contact with the substrate. The TMMs may comprise a material that exhibits an electrical resistivity change at temperature over time. The apparatus may include a controller configured to measure the electrical resistivity of at least a portion of the TMMs, and to determine a thermal history based on the electrical resistivity measures.

Abstract: The apparatus obtains a decreasing gradient of the maximum oxygen storing quantity Cmax with respect to the increase in an air flow rate Ga on the basis of two maximum oxygen storing quantities Cmax, which are respectively estimated in case where the air flow rate Ga assumes two different values, and the two values of the air flow rate Ga. As the deterioration degree of the catalyst unit 53 increases, the decreasing gradient increases. When the deterioration degree of the catalyst unit 53 is the same, the decreasing gradient tends to be the same, even if the degree of the response of the change in the output from a downstream air-fuel-ratio sensor 67 varies. Accordingly, the obtained decreasing gradient can be a value correctly indicating the deterioration degree of the catalyst unit 53.

Abstract: A method to operate an internal combustion engine by derating the engine in response to sensed emissions levels as compared to engine speed and engine torque and logging a fault.

Abstract: A method for determining malfunction of a nitrogen oxide sensor compares a nitrogen oxide amount detected by the sensor with a predetermined value of nitrogen oxide. If the difference between the predetermined value and the amount detected by the sensor is within a predetermined range, the method determines whether an engine is in a steady state. If the engine is in a steady state, the method changes one or more engine control parameters, thereby varying an actual nitrogen oxide amount. After changing the parameters, the method determines whether the amount detected by the sensor changes. The method determines that the sensor is malfunctioning if the amount detected by the sensor does not change. A selective catalytic reduction system includes a first nitrogen oxide sensor, a selective catalytic reduction apparatus, and a second nitrogen oxide sensor, all disposed in an exhaust pipe. A control portion performs the above-described method.

Abstract: The exhaust gas purifying catalysts sometimes generate H2S which emits exhaust odor under reducing atmosphere. However, in the ordinary air-fuel ratio control, it takes much time to establish sufficient oxygen atmosphere for suppressing H2S emission when the maximum oxygen storage amount which the exhaust gas purifying catalyst can store is large. Thus, the fuel cut control apparatus of an internal combustion engine executes fuel cut to bring oxygen in the exhaust gas into an excessive state when the maximum oxygen storage amount is a predetermined amount or more. As a result, sufficient oxygen can be stored in the exhaust gas purifying catalyst. Even when the maximum oxygen storage amount of the exhaust gas purifying catalyst is smaller than the predetermined amount, if the temperature of the exhaust gas purifying catalyst is lower than predetermined temperature, fuel cut is executed.

Abstract: An engine control system that regulates fuel to an engine after lean idle operation includes a first module that determines a rich mass fuel rate based on a lean operation mass air flow and a stoichiometric air to fuel ratio (AFR) and that calculates a time rich based on the rich mass fuel rate. A second module regulates fuel to the engine during a rich operation period after the lean idle operation to provide the rich mass fuel rate for the time rich.

Abstract: A diagnostic system for an exhaust system including a catalyst and a post-catalyst oxygen sensor is provided. The system generally includes a fuel control module that commands fuel to transition from a rich condition to a lean condition and that commands fuel to transition from the lean condition to the rich condition. A first diagnostic module monitors the post-catalyst oxygen sensor during the transition from the rich condition to the lean condition. A second diagnostic module monitors the catalyst during the transition from the lean condition to the rich condition.

Abstract: A system that diagnoses regeneration of an electrically heated particulate filter is provided. The system generally includes a grid module that diagnoses a fault of the grid based on at least one of a current signal and a voltage signal. A diagnostic module at least one of sets a fault status and generates a warning signal based on the fault of the grid.

Abstract: An exhaust system may include a canister that is disposed downstream from an engine. A particulate filter (PF) is disposed within the canister and filters particulates within an exhaust from the engine. A reducing catalyst is disposed within the canister, is on the PF, and promotes reaction of a liquid reductant in the exhaust after reception by the PF. A heating element is disposed within the canister and heats particulate matter in the PF.

Abstract: An internal combustion engine has a plurality of cylinders and an exhaust tract into which a mixture which is situated in the respective cylinder is introduced in the respective discharge strokes. A combustion misfire rate is determined as a function of at least one operating variable of the internal combustion engine. A temperature in the exhaust tract is determined as a function of the combustion misfire rate.

Abstract: A monitoring method and a monitoring arrangement, wherein: (a) first comparison value is established based on information from a sensor as to the measured magnitude of a parameter related to exhaust gases flowing out of an exhaust gas aftertreatment appliance included in an exhaust aftertreatment system; b) a second comparison value corresponding to the first comparison value is established based on a value representing the magnitude of said parameter calculated on the basis of a calculation model; c) a difference value representing the difference between said comparison values is established; d) steps a)-c) are repeated during a certain period of time and a variance value representing the variance of the difference value during this period of time is established; and e) the variance value is compared with a given threshold value for generation of information regarding the functioning of the sensor or the system.

Abstract: An exhaust gas purification system determines a deposited state of particulate matters based on a differential pressure across a diesel particulate filter (DPF) sensed by a differential pressure sensor. An electronic control unit (ECU) of the system prohibits the determination of the deposited state of the particulate matters, which is performed based on the differential pressure, when uniformity of temperature distribution inside the DPF is low. The ECU estimates temperatures at multiple points inside the DPF distant from an inlet along a direction of a flow of exhaust gas based on the temperature at the inlet sensed by an exhaust gas temperature sensor disposed immediately upstream of the DPF. The ECU determines the uniformity of the temperature distribution inside the DPF based on a range of the temperatures at the multiple points.

Abstract: The invention is a method for diagnosing operation of a nonthermal plasma discharge device and a lean NOx trap disposed in the exhaust of an internal combustion engine. The method further includes reducing power to the nonthermal plasma discharge device and determining that the nonthermal plasma discharge device is operating properly when a concentration of NOx of exhaust gases exiting the lean NOx trap increases in response to reducing power to the nonthermal plasma discharge device. Additionally, the nonthermal plasma discharge device is found not to be operating when the NOx concentration remains substantially constant in response to a decrease in power supplied to the nonthermal plasma discharge device.

Abstract: A secondary air supply system includes a supply passage, a valve, and a detecting unit. Secondary air is supplied to the upstream of a purification apparatus in an exhaust passage of an engine through the supply passage. The valve communicates and blocks the supply passage to be in open and close conditions. The detecting unit detects a detection object of secondary air in the upstream of the valve in the supply passage. A diagnosis apparatus for the secondary air supply system includes a diagnosis unit that obtains a detection result of the detecting unit in each of the open and close conditions of the valve for evaluating an abnormity of the secondary air supply system in accordance with the detection result. The diagnosis apparatus includes a reliability maintaining unit that determines the diagnosis operation of the diagnosis unit to be valid when the detecting operations in the open and close conditions are continuously performed.

Abstract: A deterioration diagnosis system for an air fuel sensor mounted to an exhaust pipe of an internal combustion engine. The air fuel sensor determines a mixture ratio of air and fuel fed into the internal combustion engine. In the system, an inclination of an output signal of the air-fuel ratio sensor is calculated; variance of the inclination is calculated; deterioration of the air-fuel ratio sensor is determined based on the variance of the inclination.

Abstract: A sensor for use with a diesel particulate filter in an exhaust system includes a collection device configured to be positioned downstream of the diesel particulate filter such that particulate matter not captured by the diesel particulate filter accumulates on the collection device. The collection device is configured to visually indicate a rate of particulate matter accumulation on the collection device. The rate of particulate matter accumulation corresponds to filter performance.

Abstract: An unburned fuel supply section performs temperature rise control to supply fuel to an oxidizing catalyst disposed upstream of an exhaust purification device to cause temperature rise of the exhaust purification device using heat generated in oxidation reaction of fuel on the catalyst. During the temperature rise control, an actual cumulative fuel quantity calculation section obtains actual cumulative fuel quantity by accumulating the amount of fuel supplied to the catalyst. A theoretical cumulative fuel quantity calculation section calculates fuel supply quantity required for temperature rise of the exhaust purification device on the premise that oxidation performance of the catalyst is not deteriorated, and obtains theoretical cumulative fuel quantity by accumulating the calculated fuel supply quantity.

Abstract: A diagnostic apparatus for an internal combustion engine is disclosed herein. In one embodiment, the diagnostic apparatus comprises a catalytic converter and a controller. The catalytic converter is disposed in an exhaust passage of an engine and treats an exhaust gas component in the exhaust gas. The controller is adapted to perform a number of functions. More specifically, the controller is adapted to operate the engine with an engine control parameter to increase catalyst temperature of the catalytic converter during a cold engine condition. The controller is further adapted to calculate a temperature factor indicative to temperature increase of the catalyst based on the engine control parameter. The controller is further adapted to estimate the amount of the exhaust gas component flowing out of the catalytic converter based on the temperature factor.

Abstract: A system and method for estimating the effect of forced regeneration of a diesel particulate filter (22) by post-injection of fuel on fuel dilution of engine motor oil.

Abstract: A method of controlling an internal combustion engine system. The method comprises supplying a first amount of electric energy to heat to an upstream sensor located in an exhaust gas passage upstream of an exhaust gas after-treatment device and adjusting an air-fuel mixture supplied to the internal combustion engine based on an output of the upstream sensor during a first engine operating condition, and supplying a second amount of electric energy, which is smaller than the first amount, to heat the upstream sensor and adjusting the air-fuel mixture based on an output of a downstream sensor located in the exhaust gas passage and downstream of the exhaust gas after-treatment device during a second engine operating condition.

Abstract: In a device for restraining the deterioration of a catalytic apparatus of an internal combustion engine of the present invention, when the temperature of the catalytic apparatus arranged in the engine exhaust system is higher than a predetermined temperature in a vehicle deceleration, a fuel-cut of the engine is prohibited and a first motor-generator MG2 connected with the vehicle drive shaft 6 is operated as a generator to charge an electrical accumulator 8.

Abstract: To provide an apparatus for evaluating the deterioration condition of a catalyst of an internal combustion engine that can improve the accuracy of an evaluation of the deterioration condition of a catalyst and can suppress a worsening of emissions. The apparatus forcedly sets the air/fuel ratio upstream of a catalyst provided in an exhaust system of an internal combustion engine at a rich condition or a lean condition on the basis of a detected value of a sub O2 sensor downstream of the catalyst in the internal combustion engine and evaluates the deterioration condition of the catalyst.

Abstract: A NOx trapping catalytic converter diagnostic apparatus basically has a particulate matter accumulation estimating component, a particulate matter accumulation detecting component and a deterioration determining component. The particulate matter accumulation estimating component is configured to estimate an estimated amount of particulate matter accumulated a particulate matter filter that is positioned downstream of a NOx trapping catalytic converter. The particulate matter accumulation detecting component is configured to detect a detected amount of particulate matter accumulated in the particulate matter filter. The deterioration determining component is configured to determine if deterioration of the NOx trapping catalytic converter has occurred based on the estimated amount of accumulated particulate matter and the detected amount of accumulated particulate matter without using a NOx sensor to determine if the NOx trapping catalytic converter has deteriorated.

Abstract: Provided are an exhaust treatment catalyst and an exhaust article containing the catalyst. The catalyst comprises a carrier; a first layer deposited on the carrier, said first layer comprising substantially only at least one refractory metal oxide; a second layer deposited on the first layer, said second layer comprising substantially only at least one oxygen storage component and at least one binder therefore; and a third layer deposited on the second layer, said third layer comprising at least one layer of one or more platinum group metal components supported on a refractory metal oxide support.

Abstract: A diagnostic system in which the accuracy of the diagnosis of the deterioration state of a catalyst in a catalytic converter for cleaning the exhaust gas of an internal combustion engine is enhanced without incurring a rise in cost. The temperature of the catalyst is estimated using the operating-state signal (for example, the flow rate of intake air or the width of a fuel injection pulse) of the engine by a diagnostic device. The conversion efficiency of the catalyst calculated from the outputs of oxygen sensors is corrected using the estimated temperature by the diagnostic device. The deterioration state of the catalyst is diagnosed on the basis of the corrected temperature by the diagnostic device.

Abstract: A diesel engine exhaust gas after-treatment device comprising a first temperature sensor that detects the temperature either upstream or downstream from a filter as a first temperature and detects the filter's other temperature as a second temperature, and a microcomputer. The microcomputer calculates the filter's hypothetical bed temperature from the temperature of either of the first and second temperatures; calculates the heat radiation coefficient from the filter to the external atmosphere according to the exhaust gas flow rat; and calculates the second temperature's estimated temperature based on the heat radiation coefficient and the above-described one first temperature. The filter's estimated bed temperature is found based on the above-described hypothetical bed temperature and the above-described detected second temperature and the above-described second temperature's estimated temperature. The microcomputer regenerates the filter based on the estimated bed temperature.

Abstract: A diagnostic device of an internal combustion engine diagnoses a condition of a differential pressure sensor. The sensor in a normal condition detects a differential pressure of an exhaust gas between upstream and downstream sides of a diesel particulate filter disposed in an exhaust system of the engine. The sensor in a fault condition detects no differential pressure of the exhaust gas. The device has a block obtaining a first signal from the sensor when the engine is operated in a low flow rate region of the exhaust gas and obtaining a second signal from the sensor when the engine is operated in a high flow rate region of the exhaust gas. A diagnostic block of the device judges from a difference between levels of the first and second signals whether the sensor is in the normal or fault condition.