Methods and systems are provided for detecting exhaust gas oxygen sensor degradation due to sealant off-gassing. In one example, a method may include indicating exhaust gas oxygen sensor degradation due to sealant off-gassing responsive to a change in fueling demand without a change in driver-demanded torque after a threshold exhaust temperature has been reached. In response to the indication, a measurement correction may be learned and applied to measurements of the exhaust gas oxygen sensor in order to accurately determine an air-fuel ratio of the exhaust.

A delay module, based on a base request received for a first loop, sets a delayed base request for a second loop. A first period between the first and second loops corresponds to: a first delay period of an oxygen sensor; and a second delay period for exhaust to flow from a cylinder of an engine to the oxygen sensor. A closed loop module determines a closed loop correction for the second loop based on: the delayed base request for the second loop; a measurement from the oxygen sensor; the closed loop correction for the first loop; and the closed loop correction for a third loop. A second period between the second and third loops corresponds to the first delay period of the oxygen sensor. A summer module sets a final request for the second loop based on the base request plus the closed loop correction for the second loop.

Systems and methods for determining fuel delay in a fuel injected engine with cylinders that may be deactivated are presented. In one example, the fuel injection delay is determined via a cylinder firing schedule array when the cylinder firing schedule array is available. The fuel injection delay is determined via weighted average of a fuel injection delay of a present engine cycle and a fuel injection delay of a past engine cycle when the cylinder firing schedule array is not available.

A method of controlling a fuel injection quantity using a lambda sensor may include performing a lambda deviation learning mode by controlling a lambda deviation, due to a difference between a lambda model value and a lambda sensor measurement value, by a controller during engine combustion in which an engine RPM and a fuel injection quantity are detected, wherein, in the lambda deviation learning mode, a learning map is learned and is then updated by setting a fuel correction quantity depending on the lambda deviation as a learning value, and a fuel injection quantity is determined, in consideration of the fuel correction quantity depending on an RPM and a fuel quantity based on the updated learning map, and is output as an output value, so that the output value is applied to feedback control for a next fuel injection quantity.

A delay module, based on a base request received for a first loop, sets a delayed base request for a second loop. A first period between the first and second loops corresponds to: a first delay period of an oxygen sensor; and a second delay period for exhaust to flow from a cylinder of an engine to the oxygen sensor. A closed loop module determines a closed loop correction for the second loop based on: the delayed base request for the second loop; a measurement from the oxygen sensor; the closed loop correction for the first loop; and the closed loop correction for a third loop. A second period between the second and third loops corresponds to the first delay period of the oxygen sensor. A summer module sets a final request for the second loop based on the base request plus the closed loop correction for the second loop.

A sensor system (1, 1S) including a current DA converter (42) outputting a control current (Ip) of a sensor element (3S), a control unit (4C) generating a control current instruction value (Ipcmd) corresponding to magnitude of the control current and inputting this instruction value to the current DAC, an instruction value sequence generating unit (47) generating, instead of the control current instruction value, an inspection instruction value sequence (RChcmd) in which predetermined inspection current instruction values (Chcmd) inputted to the current DAC are arranged in order and by which failure of the current DAC can be detected, an inspection current detection unit (71) detecting an inspection current value (Ichv) of an inspection current (Ich) outputted from the current DAC, and a failure detection unit (8) detecting failure of the current DAC from an inspection current value sequence (RIchv) in which the inspection current values are arranged in order of detection.

An air-fuel ratio region detection unit, including a first determination voltage higher than a target voltage value indicating the stoichiometric air-fuel ratio, and a second determination voltage lower than the target voltage value, determines that an air-fuel ratio of an engine is within a first rich region when an oxygen sensor output equals or exceeds the first determination voltage, determines that the air-fuel ratio is within a second rich region when the oxygen sensor output equals or exceeds the target voltage value but is lower than the first determination voltage, determines that the air-fuel ratio is within a second lean region when the oxygen sensor output equals or exceeds the second determination voltage but is lower than the target voltage value, and determines that the air-fuel ratio is within a first lean region when the oxygen sensor output is lower than the second determination voltage.

An ECU acquires a fluid temperature, a coolant temperature and a soak time, and determines whether vapors have been produced in a fuel supply device on the basis of a vapor production prediction map. When the ECU determines that vapors have been produced in the fuel supply device, the ECU reduces a feedback gain. Subsequently, the ECU predicts a vapor production time, and, when the ECU determines that a vapor production end time has been reached, executes normal feedback control.

An air-fuel ratio region detection unit, including a first determination voltage higher than a target voltage value indicating the stoichiometric air-fuel ratio, and a second determination voltage lower than the target voltage value, determines that an air-fuel ratio of an engine is within a first rich region when an oxygen sensor output equals or exceeds the first determination voltage, determines that the air-fuel ratio is within a second rich region when the oxygen sensor output equals or exceeds the target voltage value but is lower than the first determination voltage, determines that the air-fuel ratio is within a second lean region when the oxygen sensor output equals or exceeds the second determination voltage but is lower than the target voltage value, and determines that the air-fuel ratio is within a first lean region when the oxygen sensor output is lower than the second determination voltage.

Various approaches are described for air-fuel ratio control in an engine. In one example, a method include adjusting fuel injection from an anticipatory controller responsive to exhaust oxygen feedback of an exhaust gas sensor positioned upstream of an exhaust catalyst, the anticipatory controller including a first integral term and a second integral term, the second integral term correcting for past fuel disturbances. In this way, it is possible to provide fast responses to errors via the anticipatory controller, while corrected known past fueling errors, on average, via the second integral term.