US Patent 11287354 Systems for diagnostics of a variable displacement engine

Methods and systems are provided for diagnostics of a cylinder valve actuation mechanism in a variable displacement engine (VDE). In one example, during an engine-off condition, the engine may be rotated unfueled, via a starter motor, and a reference exhaust air flow may be estimated. One or more deactivatable engine cylinders may then be deactivated and degradation of the cylinder valve actuation mechanism may be indicated based on a difference between the exhaust air flow following the cylinder deactivation and the reference exhaust air flow.