Patent ID: 7778766

Claim:
An engine system, comprising: a position control module that changes a position of at least one of a camshaft phaser and an exhaust gas recirculation (EGR) valve based on a first nitrogen oxide (NOx) level in an exhaust gas produced by an engine; a NOx estimation module that estimates an amount of NOx in the exhaust gas within a predetermined period after the change of position of at least one of the camshaft phaser and the EGR valve, wherein the estimated amount of NOx is based on a plurality of predetermined NOx amounts corresponding to a plurality of changes of position of at least one of the camshaft phaser and the EGR valve; and a diagnostic module that determines a state of at least one of the camshaft phaser and the EGR valve based on a predetermined threshold and a difference between the estimated amount of NOx and a second NOx level, wherein the first and second NOx levels are measured using a NOx sensor.