Abnormality detection device for exhaust gas recirculation apparatus

Abstract

An abnormality detection device for an exhaust gas recirculation apparatus is provided that can perform abnormality detection with respect to an EGR valve while suppressing the influence of a size relationship between an intake pressure and an exhaust pressure. An ECU (Electronic Control Unit) executes processing for extracting a pulse from an intake pipe pressure value. The ECU executes arithmetic processing for performing Fast Fourier Transform (FFT) with respect to an output waveform of an intake pressure sensor obtained by sampling processing, and also executes extraction processing that extracts a 'frequency component corresponding to a period of an exhaust pulse'. The ECU executes processing that determines, in steps, whether or not the size of the extracted pulse (amplitude size) exceeds a threshold value. If the amplitude size exceeds the threshold value, the ECU executes processing that determines that a totally closed abnormality is occurring in the EGR valve.