Patent ID: 8825348

Claim:
An exhaust gas purification system comprising: an exhaust gas source; an exhaust gas passageway configured to route a flow of exhaust gas from the exhaust gas source to an intake portion of the exhaust gas source; a cooling system being flow coupled with the exhaust gas passageway positioned at a location upstream of the exhaust gas source and downstream of the intake portion of the exhaust gas source and operable to transfer heat from the flow of exhaust gas to a coolant in flow communication with the cooling system; a bypass passageway flow coupled with the exhaust gas passageway and bypassing the cooling system; an exhaust gas recirculation valve in the exhaust gas passageway that is in flow communication with and downstream of the cooling system and the bypass passageway, wherein the exhaust gas recirculation valve is operable to selectively modulate a flow rate of cooled exhaust gas from the cooling system to the intake portion, wherein the exhaust gas recirculation valve is connected with a stepper motor that is operable to open and close the exhaust gas recirculation valve; a bypass valve operable to control flow through the bypass passageway and the cooling system; at least one valve operation sensor connected to the exhaust gas recirculation valve; and a controller operable to control the bypass valve to direct the flow of exhaust gas to the bypass passageway and bypass the cooling system to heat the exhaust gas recirculation valve during exhaust gas recirculation based on a signal from the valve operation sensor, wherein the controller is configured to detect a contamination condition of the exhaust recirculation valve in response to a signal from the at least one valve operation sensor indicating a number of incremental steps to open or close the exhaust gas recirculation valve exceeds a predetermined number of steps and to control the bypass valve to bypass the cooling system and direct the flow of exhaust gas to the bypass passageway to heat the exhaust gas recirculation valve in response detection of the contamination condition.