An abnormality diagnosis system of limit current type air-fuel ratio sensors comprises a current detecting part and a sensor temperature control device. The abnormality diagnosis system uses the current detecting part to detect the output current of the air-fuel ratio sensor when the air-fuel ratio is made the rich air-fuel ratio in the state where temperature of the air-fuel ratio is made the first temperature and when the air-fuel ratio is made the rich air-fuel ratio in the state where the temperature of the air-fuel ratio is made a second temperature higher than the first temperature. It is judged that the air-fuel ratio sensor is abnormal if the output current when the temperature of the air-fuel ratio sensor is the first temperature is larger than the output current when it is the second temperature by a predetermined value or more.

A method of diagnosing a knock sensor includes steps of receiving data from the knock sensor, the knock sensor configured to be coupled to an engine, processing the data to derive one or more events from the data, and determining whether the one or more events took place at a known time or a known crank position.

It is intended to, when abnormality in either one of two rotation detection sections with different detection frequencies occurs, quickly and highly accurately detect the abnormality to favorably deal with abnormality occurring during low engine rotation. It is determined that abnormality is present in the rotation phase detection section, when an absolute value of difference between an actual VTC angle detected by a rotation phase detection section and an integrated value of a VTC change angle detected by motor rotation sensor 201 with the higher detection frequency than the frequency of detection of the actual VTC angle by the rotation phase detection section is equal to or greater than a predetermined value.

A method for diagnosing a variable valve timing system configured for enhancing precision of diagnosis regarding a variable valve timing system by precisely diagnosing whether an oil pressure detecting device of the variable valve timing system normally operates, may include a normal operation time determining operation of determining a normal operation time of an oil pressure detecting device to determine whether the oil pressure detecting device is normal after an engine starts, and a diagnosing operation of diagnosing whether the oil pressure detecting device is normal according to whether the oil pressure detecting device of the VVT system is turned off within the normal operation time or whether oil pressure reaches reference pressure.

An internal combustion engine comprises an exhaust purification catalyst and an air-fuel ratio sensor arranged at a downstream side of the exhaust purification catalyst, stops or decreases a feed of fuel as fuel cut control, and controls an air-fuel ratio of exhaust gas to a rich air-fuel ratio after the end of the fuel cut control as post reset rich control. The diagnosis system calculates a first characteristic of change of air-fuel ratio at the time when the output air-fuel ratio first passes a first air-fuel ratio region leaner than a stoichiometric air-fuel ratio and a second characteristic of change of air-fuel ratio at the time when the output air-fuel ratio first passes a second air-fuel ratio region including a stoichiometric air-fuel ratio. The diagnosis system diagnoses the abnormality of the air-fuel ratio sensor based on the first characteristic of change of air-fuel ratio and the second characteristic of change of air-fuel ratio. As a result, it is possible to suppress the effects of the change of state of the exhaust purification catalyst while accurately diagnosing the abnormality of deterioration of response of a downstream side air-fuel ratio sensor.

A direct fuel injection internal combustion engine fluidly coupled to an exhaust aftertreatment system is described and includes a plurality of fluidly coupled exhaust purifying devices and an exhaust gas sensor. A method of controlling the engine includes, activating, via a heater controller, a heating element of the exhaust gas sensor in response to starting the internal combustion engine. An exhaust gas feedstream is monitored to determine a temperature of the exhaust gas sensor. Engine control to effect heating of one of the exhaust purifying devices is permitted only when a temperature of the exhaust gas sensor is greater than a threshold temperature.

Methods and systems are provided for generating a predictive tachometer profile at a tachometer of a vehicle. An engine speed offset can be generated based on an engine acceleration and an accelerator pedal position rate. A predictive tachometer profile displayed at the tachometer can then be generated based on the engine speed offset and an actual engine speed.

A constant current circuit is controlled to stop a constant current Ics (Ics=0) flowing between sensor electrodes of an oxygen sensor, in a period before the oxygen sensor becomes active, during a fuel cut of an engine, and after the engine stops. When an abnormality (for example, a failure) occurs in the constant current circuit, a sensor output equivalent to an output of the oxygen sensor of when the constant current circuit is controlled to stop the constant current Ics is different from a normal sensor output. An abnormality diagnosis is executed to determine a presence or absence of the abnormality in the constant current circuit depending on whether the output of the oxygen sensor is out of a predetermined normal range, in a period before the oxygen sensor becomes active, during a fuel cut of an engine, and after the engine stops (when the constant current circuit is controlled to stop the constant current Ics).

Methods and systems are provided for determining barometric pressure. In one example, an onboard vacuum pump is utilized to draw a vacuum at a constant flow rate across a reference orifice, and the resulting vacuum level is converted to a barometric pressure. In this way, other sensors for determining barometric pressure in a vehicle may be rationalized without the use of engine operation, and in an example where the other sensors for determining barometric pressure are not functioning as desired, barometric pressure as inferred from the onboard pump may be utilized to adjust engine operation.

A diagnostic device for a sensor 100 provided in an exhaust passage 11 of an internal combustion engine 10 of a vehicle and detecting nitrogen compounds in exhaust gas, the diagnostic device including an offset diagnosis unit 42 which diagnoses, during deceleration of the vehicle in which the internal combustion engine 10 stops fuel injection, an offset amount of a sensor value of the sensor 100 from a zero point based on the sensor value of the sensor value, and a diagnosis prohibition unit 44 which prohibits the diagnosing of the offset amount when a flow rate of the exhaust gas of the internal combustion engine 10 rapidly increases while the offset amount is diagnosed by the offset diagnosis unit 42.