| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for determining a fault state in an exhaust gas recirculation(EGR) system. SOLUTION: An EGR valve is opened (64), and temperature of an EGR cooler is detected while the EGR valve is open, thereby generating a temperature signal (66). A symmetry signal is generated from the temperature signal, and a frequency component of the symmetry signal is separated by carrying out frequency analysis to the symmetry signal. A magnitude of the main frequency component is evaluated and when the magnitude is out of a diagnostic threshold value, a fault state in an EGR system is indicated. |
