Variable valve lift diagnostic systems and methods using cam phaser differential oil pressure

A diagnostic system for a vehicle, comprising:

• a difference module that determines pressure differences for a camshaft revolution based on differences between:
• first pressures within a first chamber of a camshaft phaser measured at a plurality of times during the camshaft revolution using a pressure sensor, wherein the first pressures within the first chamber control advancement of the camshaft relative to a crankshaft of an engine;
• and
• second pressures within a second chamber of the camshaft phaser measured at the plurality of times during the camshaft revolution using the pressure sensor, wherein the second pressures within the second chamber control retardation of the camshaft relative to the crankshaft of the engine;
• a Fourier module that performs a Fourier Transform (FT) based on the pressure differences to produce FT data;
• and
• a fault module that, based on the FT data, selectively indicates that a fault is present in a variable valve lift mechanism that is actuated by the camshaft and that illuminates a malfunction indicator light (MIL) when the fault is present in the variable valve lift mechanism.