Failure diagnosis device for an EGR control system

A failure diagnosis device for an EGR control system, said device comprising:

• a) an exhaust gas recirculation control means for opening and closing an exhaust gas recirculation pipe which recirculates exhaust gas at an exhaust pipe of an engine to an intake pipe thereof;
• b) detecting means for detecting a predetermined running condition of the engine;
• and
• c) control device which inputs values of predetermined parameters signifying the predetermined running condition of the engine at each of a plurality of recurring first predetermined times, said control device;
• i) calculating differences between preceding input values and current input values,
• ii) accumulating the differences,
• iii) determining the exhaust gas recirculation control means to be normal when the accumulated value is equal to or greater than a predetermined value when a second predetermined time has elapsed from when the exhaust gas recirculation pipe is forcibly closed,
• iv) enabling the exhaust gas recirculation control means in response to a normal determination,
• v) determining the exhaust gas recirculation control means to be abnormal when the accumulated value is below the predetermined value when the second predetermined time has elapsed, and
• vi) generating an alarm in response to an abnormal determination.