Various methods and systems are provided for health assessments of a fuel system. In one example, a fuel system includes a high-pressure fuel pump operable to increase fuel pressure from a first pressure to a second pressure, a common fuel rail fluidly coupling the high-pressure fuel pump to a plurality of fuel injectors each of which is operable to inject fuel to individual cylinders of an engine, a pressure sensor operable to detect a pressure of fuel at the common fuel rail, and a controller operable to diagnose a condition of the high-pressure fuel pump based on output from the pressure sensor.

Methods and systems are provided for diagnosing a degraded fuel injector delivering undesired additional fuel in a variable displacement engine. In one example, a method includes, responsive to an indication of a cylinder air-fuel imbalance, deactivating a subset of cylinders of a multi-cylinder engine, performing a power balance test to determine an output of each cylinder after a duration of deactivation, and indicating that a deactivated cylinder has a degraded fuel injector responsive to the output being lower than a threshold output.

Methods and systems are provided for an engine. A condition of the engine may be diagnosed based on information provided by signals from a generator operationally connected to the engine and/or other signals associated with the engine. Different types of degradation may be distinguished based on discerning characteristics within the information. Thus, a degraded engine component may be identified in a manner that reduces service induced delay.

A variable compression ratio internal combustion engine is provided with a variable compression ratio mechanism in which a mechanical compression ratio of the internal combustion engine changes in accordance with a rotational position of a control shaft, a low compression ratio side stopper, a high compression ratio side stopper, a sensor for detecting a rotational position of a drive shaft of an actuator, and an arm press-fitted onto the drive shaft Relative rotation between the arm and the drive shaft occurs when a torque exceeding an upper-limit torque has been applied, The drive shaft or the control shaft is caused to move to restriction positions restricted by the respective stoppers, and then a diagnosis on the presence or absence of the relative rotation is executed, based on the detected values at the respective restriction positions.

A method for detecting a sticking tank vent valve in a motor vehicle, a temperature sensor being situated in a tank vent line between the tank vent valve and an inlet point into an intake manifold or into a turbocharger and sticking of the tank vent valve being detected when the absolute value of a correlation of a calculated tank ventilation mass flow and of a signal value of the temperature sensor violates a predefinable threshold value.

An engine system includes: an engine including a direct injection valve that injects fuel into a cylinder of the engine and a port injection valve that injects fuel into an intake port of the engine; and an electronic control unit configured to control an operation of the engine by adjusting, based on a state of the engine, a rate of fuel injection from the direct injection valve with respect to total fuel injection and a rate of fuel injection from the port injection valve with respect to the total fuel injection. The electronic control unit executes a malfunction diagnosis with the rate of fuel injection from the direct injection valve set to 100%, when the electronic control unit determines that an execution condition for executing the malfunction diagnosis on a fuel system is satisfied and a power required of the engine is equal to or greater than a prescribed power.

Example embodiments relate to a method and a control unit, wherein a drive system having an electric machine and having an internal combustion engine with at least a first cylinder and a crankshaft is provided. A fuel feed to at least the first cylinder of the internal combustion engine is deactivated, wherein the electric machine is coupled fixedly in terms of torque to the internal combustion engine. The electric machine is actuated such that the crankshaft of the internal combustion engine rotates at a predefined rotational speed, wherein a first cylinder segment time duration, which is assigned to the first cylinder, is detected. A corrective value is determined in a manner dependent on the first cylinder segment time duration.

A method and a computer program for recognizing and differentiating a flow rate error and a dynamic error of an exhaust gas recirculation system (EGR) of an internal combustion engine. Measured and modeled EGR mass flow signals are each subjected to bandpass filtering using time constants optimized for determining flow rate errors and bandpass filtering using time constants optimized for determining dynamic errors. The energy is determined for each of the filtered signals and an energy quotient is computed between the energies of the signals filtered for dynamic errors and the signals filtered for flow rate errors. A dynamic error and a flow rate error of the exhaust gas recirculation may be recognized and differentiated from one another on the basis of the energy quotients.

Systems and methods for determining air-fuel error in an engine fueled via direct and port fuel injection. Errors associated with individual fuel injection systems are distinguished from a common error based on trends in the error correction coefficients of the individual fuel injection systems. Adaptive fuel multipliers for each injection system are updated to account for the common error.

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.