Fault detecting apparatus for exhaust gas recirculation control system of internal combustion engine

A fault detecting apparatus for an exhaust gas recirculation control system of an internal combustion engine, comprising:

• an intake pipe for supplying air to said internal combustion engine;
• a throttle valve disposed in said intake pipe to be selectively opened and closed for regulating a flow of the air supplied to said internal combustion engine through said intake pipe;
• an exhaust gas recirculation pipe for introducing an exhaust gas of said internal combustion engine to said intake pipe at a location downstream of said throttle valve for recirculating the exhaust gas through said internal combustion engine;
• an exhaust gas recirculation valve disposed in said exhaust gas recirculation pipe for regulating a recirculation flow rate of the exhaust gas flowing through said exhaust gas recirculation pipe;
• sensor means for detecting operation state of said internal combustion engine, inclusive of an intake pressure, to thereby output engine operation state information;
• exhaust gas recirculation valve control means for controlling said exhaust gas recirculation valve in dependence on said operation state information supplied from said sensor means;
• fault decision enabling condition detecting means for detecting satisfaction of a decision enabling condition for enabling a decision concerning occurrence of a fault in an exhaust gas recirculation control means inclusive of said exhaust gas recirculation valve control means on the basis of said operation state information;
• enforcive valve opening/closing means for forcibly opening and/or closing said exhaust gas recirculation valve during a period in which said fault decision enabling condition is satisfied;
• and
• fault decision means for comparing a value derived from the intake pressures detected upon enforcive opening/closing of said exhaust gas recirculation valve with a fault decision reference value to thereby decide whether any fault occurs in said exhaust gas recirculation control means;
• wherein said fault decision means includes compensation means for suppressing influence of a parameter which affects said intake pressures detected upon said enforcive opening/closing of said exhaust gas recirculation valve.