A method and an apparatus including a processing circuit structured to: receive a first signal indicative of an upstream air-fuel equivalence ratio from a first sensor positioned upstream of an intake of a catalyst, the first signal defining a duty cycle, receive a second signal indicative of a downstream air-fuel equivalence ratio from a second sensor positioned downstream of the intake of the catalyst, adjust the duty cycle based at least in part on the second signal, and provide a fault signal in response to the duty cycle not meeting a duty cycle range for a predetermined period of time. A notification circuit is structured to provide a notification indicating that the second sensor is faulty in response to receiving the fault signal.

A method for estimating the ageing of an exhaust gas sensor (16) placed in an exhaust line (14) of a diesel internal combustion engine (10) of an industrial vehicle (1) includes: —acquiring (S100) an initial value of an estimated remaining lifetime (50) of the exhaust gas sensor; —measuring (S102) the time spent by the engine in each of several predefined engine operation modes during a predefined time period; —for each of the engine operation modes, calculating (S104) a lifetime loss value depending on the time spent by the engine in said engine operation mode during the predefined time period and on a predefined ageing rate associated to said engine operation mode; —updating (S106) the estimated remaining lifetime value by subtracting each calculated lifetime loss value from the initial value.

The abnormality diagnosis system 1 of a downstream side air-fuel ratio detection device 41, 42, comprises an air-fuel ratio control part 71 controlling an air-fuel ratio of an air-fuel mixture, an abnormality judgment part 72 judging abnormality of the downstream side air-fuel ratio detection device based on a characteristic of change of output of the downstream side air-fuel ratio detection device when the air-fuel ratio control part makes the air-fuel ratio of the air-fuel mixture change, and an oxygen change calculation part 73 calculating an amount of change of an oxygen storage amount of the catalyst when the air-fuel ratio control part makes the air-fuel ratio of the air-fuel mixture change. The abnormality judgment part does not judge abnormality of the downstream side air-fuel ratio detection device when the amount of change of the oxygen storage amount is less than a lower limit threshold value.

An abnormality detection device for an air-fuel ratio detection device arranged downstream of a filter is equipped with an abnormality detection unit that detects an abnormality in the air-fuel ratio detection device based on output change characteristics of the air-fuel ratio detection device during fuel cutoff control for stopping the supply of fuel to a combustion chamber of an internal combustion engine, and a combustion determination unit that determines whether or not a combustion amount of particulate matter in a filter during fuel cutoff control is larger than a predetermined amount. The abnormality detection unit prohibits detection of an abnormality in the air-fuel ratio detection device when the combustion determination unit determines that the combustion amount is larger than the predetermined amount.

An injection control device includes: a fuel injection quantity command value output unit that outputs a command value for a fuel injection quantity of a fuel injection valve; and a controller that executes current control on the fuel injection valve. The controller executes current area correction by calculating an area correction amount for an energization time to cause an integrated current value of an energization current profile and the integrated current value of a current to be equal to each other. Correction control of the current area correction is changed based on a detection signal of a cooling water temperature of an internal combustion engine.

An injection control device includes: a fuel injection quantity command value output unit that outputs a command value for a fuel injection quantity of the fuel injection valve; a fuel injection quantity correction unit that calculates an A/F correction amount and corrects the command value of the fuel injection quantity; and a controller that executes current control on the fuel injection valve. The controller executes current area correction. The injection control device further includes an area correction abnormality determination unit that determines an area correction abnormality. The area correction abnormality determination unit changes the abnormality determination value.

A method for the onboard diagnosis in a vehicle having a catalytic convertor and a lambda-controlled internal combustion engine in the running operation of the vehicle, includes determining the currently maximum possible oxygen storage capacity of the catalytic convertor as well as a measured temporal duration between the lean spike of the pre-catalyst lambda probe and the post-catalyst lambda probe takes place by means of an OSC diagnosis. The method also includes determining a theoretical residual oxygen content and determining a theoretical temporal duration. When the quotient between the measured temporal duration (Δt) and the theoretical temporal duration (Δt.sub.theo) lies within a predefined range delimited by a first and a second threshold value (SW1; SW2), thus:

[00001]$\mathrm{SW}1\le \frac{\Delta t}{\Delta t_{\mathrm{theo}}}\le \mathrm{SW}2,$

it is determined that the pre-catalyst lambda probe and the post-catalyst lambda probe operate without flaw.

A method of operating an oxygen sensor system is provided where the system includes an oxygen sensor, the oxygen sensor including a pump cell, and wherein the oxygen sensor is connected to associated circuitry such that the associated circuitry controls operation of the pump cell. The pump cell includes a pump line connected to a pump electrode of the pump cell and a return line connected to a return electrode of the pump cell. The method includes, subsequent to a diagnostic process, raising the potential of the pump line for a predetermined period of time by injecting current onto the pump line.

Systems and methods are provided for determining and correcting air/fuel imbalance between cylinders of an internal combustion engine. A deactivation strategy is determined and implemented. An evaluation is made of whether the engine is operating with an air/fuel imbalance between cylinders. When an imbalance is identified, an alternate deactivation strategy is implemented. Based on outcomes of the alternate deactivation strategy, a source cylinder of the air/fuel imbalance is identified, and fuel flow to the source cylinder is corrected.

Methods of and apparatus for monitoring the health of a fuel oxygen conversion unit for a vehicle or a vehicle engine are provided. For example, a method comprises providing a distribution of sensed values obtained from a plurality of sensors distributed along an axial length of a gas oxygen reduction unit of the fuel oxygen conversion unit and determining the health of the fuel oxygen conversion unit from the distribution. As another example, a fuel oxygen conversion unit defines a circulation gas flowpath from a fuel gas separator to a contactor and comprises a gas oxygen reduction unit positioned in the circulation gas flowpath for reducing an oxygen content of a flow of stripping gas through the circulation gas flowpath. A plurality of sensors are distributed along an axial length of the gas oxygen reduction unit.