Abstract: Methods and systems are provided for improving completion rates for engine system diagnostics for hybrid electric vehicles. In one example, a method may include in response to fueling of the engine of a hybrid electric vehicle being discontinued, establishing an air flow from an intake to an exhaust of the engine by relying on an electric motor to rotate the engine unfueled, and conducting a plurality of diagnostic monitors that rely on the air flow prior to reactivation of fueling of the engine. In this way, diagnostic monitor completion rates may be improved for hybrid electric vehicles, and fuel economy may be improved by coordinating the plurality of diagnostic monitors to be conducted during times when the engine is not fueled.

Abstract: Methods and systems are provided for detecting cylinder-to-cylinder air-fuel ratio (AFR) imbalance in engine cylinders. In one example, a method may include detecting an AFR imbalance of an engine cylinder based on an individual crankshaft acceleration of the cylinder relative to a mean crankshaft acceleration produced by all cylinders of the engine, and correcting a fuel amount of the cylinder via a fuel multiplier value, the fuel multiplier value selected from a plurality of fuel multiplier values based on an imbalance source. In this way, the AFR imbalance may be accurately detected and correcting using existing engine system sensors.

Abstract: Methods and systems are provided for improving engine torque response during transient condition. In one example, a method may include adjusting intake throttle and exhaust waste-gate valve based on the operator torque demand and concurrently, scheduling exhaust gas recirculation (EGR) and variable cam timing (VCT) based on a predicted torque shortfall ratio. The scheduling of EGR and VCT is independent of the actual position of intake throttle and exhaust waste-gate valve.

Abstract: A method and a system for indicating more than three different fluid levels in a fluid reservoir is described for a system that includes a fluid level sensor having only two output levels. In one example, the more than three different fluid levels are determined via output of the fluid level sensor and output of one or more sensors that indicate acceleration or orientation of a vehicle.

Abstract: Systems and methods for operating a vehicle that includes an engine and an electric machine are described. In one example, a speed of the engine may be adjusted so that the engine provides power to drive the electric machine without generating numerous rapid engine speed changes in a short amount of time.

Abstract: Methods and systems are provided for cycle-to-cycle torque reductions under exhaust component temperature constraints. In one example, a method may include, responsive to a torque reduction request, introducing a lambda split between two sets of cylinders over a plurality of engine cycles while maintaining an average of stoichiometry between the two sets of cylinders, and, responsive to reaching a lambda split threshold, introducing differentially delayed ignition timing in both sets of cylinders. In this way, fast torque reduction may be provided while maintaining a globally stoichiometric air-fuel ratio, thereby decreasing vehicle emissions, and reducing heat-related degradation to exhaust components.

Abstract: Systems and methods for operating a vehicle that includes a direct current to alternating current converter is described. In one example, an indication of an air flow restriction of the direct current to alternating current converter is described. The direct current to alternating current converter may supply power to devices that are external to the vehicle.

Abstract: Systems and methods for operating an engine with a plurality of deactivating valves for deactivating engine cylinders are presented. In one example, a plurality of different cylinder operating modes may be available to operate the engine. Engine fuel consumption in each of the plurality of different cylinder operating modes is estimated and the engine may be operated in the cylinder mode that provides greatest fuel efficiency.

Abstract: Methods and systems are provided for improving engine oil level sensing while a vehicle is moving. The output of a hot wire sensor partially immersed in an engine oil well is sampled during selected vehicle moving conditions when lateral and longitudinal acceleration is limited and the vehicle is driving in a straight line. A transfer function is used to correlate a rate of change in sensor output, sampled during the selected vehicle operating conditions, with engine oil level.

Abstract: Systems and methods for operating a vehicle that includes an engine and an electric machine are described. In one example, operation of the engine may be adjusted to compensate for conditions when carbon deposits may build on one or more engine spark plugs. The engine adjustments may help to remove carbon deposits from the engine's spark plugs.

Abstract: Methods and systems are provided for adjusting engine idle-stop based on operation of an on-board generator. In one example, during operation of the generator to power an external load, a method may include inhibiting engine shut-down based on input from a user.

Abstract: Systems and methods for operating an engine with deactivating and non-deactivating valves is presented. In one example, the engine may include non-deactivating intake valves, deactivating intake valves, and only non-deactivating exhaust valves. The non-deactivating exhaust valves may operate to open and close during an engine cycle while deactivating intake valves remain closed during the engine cycle to prevent air flow through selected engine cylinders.

Abstract: Systems and methods for activating and deactivating cylinders of an engine that may activate and deactivate one cylinder independent of other cylinders are presented. In one example, an engine cylinder firing fraction and a remainder value that is based on the engine cylinder firing fraction are a basis for activating and deactivating engine cylinders. The systems and methods also provide for transitioning between different cylinder firing fractions.

Abstract: Systems and methods for operating an engine with a plurality of deactivating valves for deactivating engine cylinders are presented. In one example, a plurality of different cylinder operating modes may be available to operate the engine. Engine fuel consumption in each of the plurality of different cylinder operating modes is estimated and the engine may be operated in the cylinder mode that provides greatest fuel efficiency.

Abstract: Methods and systems are providing for improving engine coolant level estimation to reduce engine overheating. The level of fluid in a coolant overflow reservoir is inferred based on the fluid level in a hollow vertical standpipe fluidically coupled to the reservoir at top and bottom locations, while the fluid level in the standpipe is estimated based on echo times of an ultrasonic signal transmitted by a sensor positioned in a recess at the bottom of the vertical standpipe. Engine power is limited differently based on distinct coolant level states determined based on a change in level of coolant in the reservoir over a duration.

Abstract: Systems and methods for operating an engine with deactivating and non-deactivating valves is presented. In one example, the engine may include non-deactivating intake valves, deactivating intake valves, and only non-deactivating exhaust valves. The non-deactivating exhaust valves may operate to open and close during an engine cycle while deactivating intake valves remain closed during the engine cycle to prevent air flow through selected engine cylinders.

Abstract: Systems and methods for operating an engine with a plurality of deactivating valves for deactivating engine cylinders are presented. In one example, a plurality of different cylinder operating modes may be available to operate the engine. Engine fuel consumption in each of the plurality of different cylinder operating modes is estimated and the engine may be operated in the cylinder mode that provides greatest fuel efficiency.

Abstract: Methods and systems are provided for using compression heating to heat a cylinder piston before cylinder combustion is resumed. Cylinder heating is achieved using combinations of slow unfueled engine rotation where the engine cylinders are heated via compression stroke heating, and slow compressor rotation where the cylinders are heated via compression heating. One or more intake or exhaust heaters may be concurrently operated to expedite cylinder heating.

Abstract: Methods and systems are provided for regenerating and purging a particulate filter of an exhaust treatment system for a combustion engine. In one example, a method may include flowing exhaust gas in a reverse direction through the particulate filter to purge particulate matter to an intake manifold of the engine for combusting. The duration of purging may be based on a regeneration achieved during a previous regeneration of the particulate filter during a deceleration fuel shut-off event.

Abstract: Methods and systems are providing for improving engine coolant level estimation to reduce engine overheating. The level of fluid in a coolant overflow reservoir is inferred based on the fluid level in a hollow vertical standpipe fluidically coupled to the reservoir at top and bottom locations, while the fluid level in the standpipe is estimated based on echo times of an ultrasonic signal transmitted by a sensor positioned in a recess at the bottom of the vertical standpipe. Engine power is limited differently based on distinct coolant level states determined based on a change in level of coolant in the reservoir over a duration.