EGR Diagnostic method and apparatus

Claim 3

Apparatus for diagnosing the operation of an exhaust gas recirculation apparatus (20-32) of an internal combustion engine (10) having an intake manifold from which a combustible mixture of air and fuel are drawn into a cylinder of the internal combustion engine to undergo combustion, and an exhaust manifold into which exhaust gases are discharged from the cylinder, the apparatus comprising the exhaust gas recirculation apparatus for recirculating a portion of the exhaust gases from the exhaust manifold into the intake manifold; a fuel delivery device (12) responsive to the speed of the internal combustion engine and the pressure in the intake manifold for supplying a quantity of fuel to the intake manifold determined to provide a desired air/fuel ratio of the combustible mixture drawn into the cylinder; and an engine control module (14) for providing a closed loop adjustment to the fuel supplied to the intake manifold by the fuel delivery device so as to establish the desired air/fuel ratio; characterised in that the engine control module tests the operation of the exhaust gas recirculation apparatus and includes a step (74) for disabling the exhaust gas recirculation apparatus; a decision point (80) for determining a change in an integral term of the closed loop adjustment to the fuel supplied to the intake manifold over a predetermined period after the exhaust gas recirculation apparatus is disabled; and a step (82) for providing an indication of a failure of the exhaust gas recirculation apparatus when the determined change in the integral term is less than a calibration value (E).

Claim 4

Apparatus for diagnosing the operation of an exhaust gas recirculation apparatus (20-32) of an internal combustion engine (10) having an intake manifold from which a combustible mixture of air and fuel are drawn into a cylinder of the internal combustion engine to undergo combustion, and an exhaust manifold into which exhaust gases are discharged from the cylinder, the apparatus comprising the exhaust gas recirculation apparatus for recirculating a portion of the exhaust gases from the exhaust manifold into the intake manifold; a fuel delivery device (12) responsive to the speed of the internal combustion engine and the pressure in the intake manifold for supplying a quantity of fuel to the intake manifold determined to provide a desired air/fuel ratio of the combustible mixture drawn into the cylinder; and an engine control module (14) for providing a closed loop adjustment to the fuel supplied to the intake manifold by the fuel delivery device so as to establish the desired air/fuel ratio; characterised in that the engine control module tests the operation of the exhaust gas recirculation apparatus and includes a step (74) for disabling the exhaust gas recirculation apparatus; a decision point (80) for determining a change in an integral term of the closed loop adjustment to the fuel supplied to the intake manifold over a predetermined period after the exhaust gas recirculation apparatus is disabled; and a step (82) for providing an indication of a failure of the exhaust gas recirculation apparatus when the determined change in the integral term is less than a calibration value (E).

Claim 5

Apparatus as claimed in Claim 2, characterised in that the engine control module (14) is responsive to the oxidizing-reducing condition of the exhaust gases for providing the closed loop adjustment; step (74) stores the value of the integral term at a time T, and disables the exhaust gas recirculation apparatus (20-32) at the time T; and decision point (80) determines the difference between the value of the integral term and the stored value of the integral term at a time spaced from the time T by an interval that allows the engine control module to adjust the fuel supplied to the intake manifold by the fuel delivery device (12) to return the air/fuel ratio to the desired air/fuel ratio.