Patent ID: 8190397

Claim:
A failure diagnosis apparatus for an exhaust pressure sensor for detecting the exhaust pressure in an exhaust gas recirculation passage which connects an exhaust passage and an intake passage of an internal combustion engine, said failure diagnosis apparatus comprising: an atmospheric pressure sensor provided separately from said exhaust pressure sensor, said atmospheric pressure sensor detects the atmospheric pressure; first determining means for making a first preliminary determination that said exhaust pressure sensor is operating in a normal state and is capable of detecting the exhaust pressure in the exhaust gas recirculation passage when said engine is in a predetermined low load operating condition and the difference between the exhaust pressure detected by said exhaust pressure sensor and the atmospheric pressure is equal to or less than a first determination threshold value; second determining means for making a second preliminary determination that said exhaust pressure sensor is operating in the normal state and is capable of detecting the exhaust pressure in the exhaust gas recirculation passage when said engine is in a predetermined high load operating condition and the difference between the exhaust pressure detected by said exhaust pressure sensor and the atmospheric pressure is equal to or greater than a second determination threshold value; and final determining means for making a final determination that said exhaust pressure sensor is operating in the normal state and is capable of detecting the exhaust pressure in the exhaust gas recirculation passage, when both of the first and second preliminary determinations are made by said first and second determining means.