Patent Document ID: 20030029233
Application ID: 09919489
Patent Flag: 0

Claim One:
1. A method for diagnosis of a gas flow restriction in the exhaust gas recirculation (EGR) system of an automotive vehicle; said vehicle comprising an engine with an intake manifold and an exhaust gas manifold, a pressure sensor for measuring the pressure of air and any exhaust gas in said intake manifold, a sensor for measuring mass air flow rate in said manifold, a sensor for determining the speed of said engine, an exhaust gas recirculation (EGR) valve and passage system for diverting engine exhaust gas from said exhaust manifold to said intake manifold, and a computer for receiving data from said sensors and controlling the flow position of said EGR valve, said method being carried out on said computer and comprising repeatedly measuring said pressure in said intake manifold, as MAPmeas, during an EGR valve diagnosis period of time, repeatedly estimating the absolute pressure in said intake manifold during said diagnosis period assuming no restriction in the flow of exhaust gas with respect to said control position, said estimates being MAP HE, repeatedly estimating the absolute pressure in said intake manifold during said diagnosis period assuming a restriction in the flow of exhaust gas through said EGR valve amounting to a defect in said EGR system, said estimates being MAP FE, and comparing the differences between values of MAPmeas taken during said diagnosis period with both of corresponding values of MAP HE and MAP FE as a passive computational basis for determining whether there is a defective restriction in said EGR system.