Methods and systems for calculating a plurality of aging factors in a system operating an engine. The calculated aging factors may include one or more of fuel injector drift, exhaust gas recirculation valve obstruction, and mass air flow sensor bias. Mass flow throughout the system, and pressures and temperatures within the system, are observed in an approach that relies on mass preservation concepts to estimate fuel injector drift, exhaust gas recirculation valve obstruction, and mass air flow sensor bias.

Methods and systems for monitoring a NOx sensor for a NOx offset value are described. In one example, the NOx offset value may be based on a minimum NOx concentration observed over an entire drive of a vehicle. The NOx offset monitor may be inhibited in response to inferring or detecting a presence of NH.sub.3 in an exhaust system.

A method for recognizing an error in a sensor signal during operation of a fuel injector of an internal combustion engine. In the method, a switch valve of the fuel injector is activated with the aid of an activation signal, and the sensor signal is detected as a signal of a sensor, which is provided for the purpose of detecting characteristic operating points of the fuel injector, in a respectively predefined time window of the sensor signal, which includes a point in time of a characteristic operating point of the fuel injector. At least one property of the sensor signal is determined, which includes a signal level and/or a rise time. It is determined, based on the at least one property of the sensor signal, whether an error is present.

Provided is a technology of accurately classifying abnormality in response characteristics of an air-fuel ratio sensors into six deterioration modes. In order to solve the above problems, the present disclosure provides a control device including a microprocessor that detects a response delay of an air-fuel ratio sensor attached to an internal combustion engine, in which the microprocessor includes a target air-fuel ratio change unit configured to change a target air-fuel ratio between lean and rich, and a response delay detection unit configured to detect a respond delay of the air-fuel ratio sensor that occurs in a real air-fuel ratio sensor signal output from the air-fuel ratio sensor when the target air-fuel ratio is changed between the lean and the rich by the target air-fuel ratio change unit.

The present invention obtains a humidity measuring device capable of performing self-diagnosis with high reliability. This humidity measuring device 20 has a diagnosis processing unit 25 for performing self-diagnosis by using gas temperatures and gas humidities before and after a gas in an ambient atmosphere to be measured is heat-controlled. The diagnosis processing unit has a diagnosis start determining unit 26 for determining whether the self-diagnosis can be started on the basis of an exchange state in the ambient atmosphere to be measured and the gas temperature and the gas humidity before the gas in the ambient atmosphere to be measured is heat-controlled, and a diagnosis continuation determining unit 28 for determining whether the self-diagnosis can be continued on the basis of the gas temperature and the gas humidity that are heat-controlled during the self-diagnosis.

A PM sensor is arranged downstream of a one-side blocked filter that collects a particulate matter in exhaust gas of an engine, and first and second sensor abnormality diagnoses are executed based on output of the PM sensor. In the first sensor abnormality diagnosis, a filter-outflow PM amount (an amount of the PM flowing out from the one-side blocked filter) is estimated based on a working condition of the engine and a PM collection rate of the one-side blocked filter, and an occurrence of output abnormality of the PM sensor is determined by comparing a sensor-detection PM amount (an amount of the PM detected based on the output of the PM sensor) with the filter-outflow PM amount. In the second sensor abnormality diagnosis, an engine discharging PM amount (an amount of the PM discharged from the engine) is estimated based on a working condition of the engine, and an occurrence of output abnormality of the PM sensor is determined by comparing an increasing rate of the output of the PM sensor with an increasing rate of the engine discharging PM amount.

An abnormality determination device is applied to an electrostatic capacitance type fuel property sensor that has a sensing section that senses an electrostatic capacitance of a fuel to be detected. The abnormality determination device of the fuel property sensor acquires a first output that is an output when a predetermined voltage is applied to the sensing section and a second output that is an output when a voltage is not applied to the sensing section. The acquired first output and second output are compared and whether or not the fuel property sensor is abnormal is determined.

A diagnosis device for an engine, the diagnosis device includes an electronic control unit. The electronic control unit is configured to execute EGR diagnosis processing to diagnose whether or not the EGR device operates normally while a vehicle is being decelerated, execute air flow meter diagnosis processing to diagnose whether or not the air flow meter is normal while the vehicle is decelerated, execute the EGR diagnosis processing after starting the air flow meter diagnosis processing, and execute the EGR diagnosis processing when the air flow meter diagnosis processing has not been completed and predetermined conditions that a duration of deceleration of the vehicle being shorter than a diagnosis time that is required to execute the air flow meter diagnosis processing are fulfilled.

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.