Methods and systems are disclosed for operating an engine that includes a knock control system. The method and system may increase opportunities to learn one or more engine knock background noise levels via changing poppet valve timing and/or fuel injection timing. The method and system may also improve knock detection if knock sensor degradation is suspected.

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 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.

A diagnostic engine calibration module is provided that is structured to diagnose a vehicle system by causing the vehicle system to operate outside of one or more calibration parameters. The diagnostic engine calibration module includes a diesel particulate filter (DPF) pressure module structured to determine a pressure differential across a DPF of an engine of the vehicle system and compare the determined pressure differential against a plurality of predetermined fault thresholds to diagnose the DPF, the plurality of predetermined fault thresholds including a predetermined minimum pressure threshold and a predetermined maximum pressure threshold.

A method for controlling starting of a vehicle upon a failure of a camshaft position sensor includes performing a fuel injection and ignition at a particular timing for starting an engine of the vehicle; measuring a battery voltage of the vehicle after the performing of the fuel injection and ignition for starting the engine; and when the battery voltage rises over a predetermined value, determining that the fuel injection and the ignition are performed at a normal timing.

An accelerator position detection device facilitates detection of a neutral position of a handlebar grip turnable in not only a positive direction but in a negative direction from the neutral position. In the accelerator position detection device provided with a detector that outputs voltage according to an angle of the handlebar grip and detects an angle for control for controlling a vehicle based upon the angle of the handlebar grip on the basis of the output of a first sensor and a second sensor, the first sensor is configured so that the first sensor outputs first voltage rising in volume from a position exceeding a first rise start angle located in a normal rotation direction by predetermined quantity from the neutral position in the normal rotation direction, and the second sensor is configured so that the second sensor outputs second voltage rising in volume from a position exceeding a second rise start angle located in a reverse rotation direction by predetermined quantity from the neutral position in the normal rotation direction.

A method of predicting temperature of at least one location in a fluid flow system that has a heating system for heating fluid. The method includes obtaining a mass flow rate of fluid flow of the fluid flow system, obtaining at least one of a fluid outlet temperature and a fluid inlet temperature of a heater of the heating system, obtaining power provided to the heater, and calculating temperature at the at least one location based on a model of the fluid flow system and the obtained mass flow rate, fluid outlet temperature, and fluid inlet temperature.

A method of detecting misfire in a combustion engine of a motor vehicle engine includes measuring a speed of a crankshaft, calculating a modal coefficient for each cylinder of the combustion engine, and indicating a misfire for at least one of the cylinders based on the calculation of the modal coefficients.

A method for controlling stabilization of an exhaust gas recirculation (EGR) gas supply may include executing an intake detector condensation stuck resolving mode including, when output abnormality of an intake detector provided at an intake manifold and a variation amount of an EGR rate of an EGR system are detected by a controller while the EGR system is operated, stopping an operation of an EGR valve of the EGR system and then re-operating the EGR valve to resolve abnormality of the intake detector, which is caused by condensation of the EGR gas which is supplied to the intake manifold.

An apparatus includes a sensor module, an offset diagnostic module, and a notification module. The sensor module is in operative communication with a cylinder pressure sensor and structured to acquire cylinder pressure data from the cylinder pressure sensor indicative of an actual in-cylinder pressure of a cylinder of an engine. The offset diagnostic module is structured to interpret the cylinder pressure data to determine an offset of the cylinder pressure sensor based on a reference in-cylinder pressure and the actual in-cylinder pressure. The notification module is structured to provide an offset error notification responsive to the offset being greater than a threshold offset.