Abstract: Temperatures of intake-air temperature, intercooler outlet temperature and intake manifold temperature sensors are compared in cold time of an engine to determine any characteristic abnormality of the sensors. A first temperature difference is obtained from temperatures of the intercooler outlet temperature sensor before and after increase in boost pressure to determine any characteristic abnormality of the intercooler outlet temperature sensor. A second temperature difference is obtained from temperatures of the intake manifold temperature and intercooler outlet temperature sensors after opening an EGR valve to determine any characteristic abnormality of the intake manifold temperature sensor.

Abstract: An EGR device for an internal combustion engine returns an EGR gas from an exhaust passage to an intake passage of an engine. The EGR device is configured to determine a target EGR ratio from an engine rotation number and an engine load and calculate an estimate EGR ratio from an intake air amount to the engine and a cylinder intake gas amount to detect a response delay of the EGR gas from a difference between the target and estimate EGR ratios.

Abstract: Temperatures of intake-air temperature, intercooler outlet temperature and intake manifold temperature sensors are compared in cold time of an engine to determine any characteristic abnormality of the sensors. A first temperature difference is obtained from temperatures of the intercooler outlet temperature sensor before and after increase in boost pressure to determine any characteristic abnormality of the intercooler outlet temperature sensor. A second temperature difference is obtained from temperatures of the intake manifold temperature and intercooler outlet temperature sensors after opening an EGR valve to determine any characteristic abnormality of the intake manifold temperature sensor.

Abstract: An EGR device for an internal combustion engine has an EGR means to return an EGR gas from an exhaust passage to an intake passage of an engine. The EGR device is configured to determine a target EGR ratio from an engine rotation number and an engine load and calculate an estimate EGR ratio from an intake air amount to the engine and a cylinder intake gas amount to detect a response delay of the EGR gas from a difference between the target and estimate EGR ratios.