Patent ID: 8380423

Claim:
A diagnostic system for an engine comprising: a phaser control module that commands a first cam phaser position of a cam phaser of said engine for a first period and a second cam phaser position of said cam phaser for a second period; and a phaser diagnostic module that: diagnoses a phaser control error for said cam phaser based on a first pressure of fluid supplied by an oil control valve (OCV) to said cam phaser measured during said first period, and a second pressure of fluid supplied by said OCV to said cam phaser measured during said second period, distinguishes a mechanical fault in said cam phaser from a hydraulic fault in said cam phaser by comparing a difference between said first pressure and said second pressure to a predetermined threshold, detects a mechanical fault in said cam phaser when said difference is greater than said predetermined threshold, and detects a hydraulic fault in said cam phaser when said difference is less than or equal to said predetermined threshold.