| 摘要 |
An apparatus detects occurrence of a fault in an exhaust gas recirculation (EGR) control system of an internal combustion engine. An intake air amount is changed by a predetermined quantity, which is determined in dependence on an operation state of the engine, when an EGR control valve is temporarily opened or closed. A determination is made as to whether a pressure within an intake pipe of the engine has changed after opening or closing of the EGR control valve. On the basis of the result of the above determination, occurrence of a fault in the EGR control system is determined. Regardless of resolution of an A/D converter which is employed in the EGR control system for performing A/D conversion of an analog signal indicative of a sensed intake air pressure, a fault thereof can be detected with high accuracy.
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