FAULT DETECTION METHOD

摘要

With a precondition that a cooling water temperature sensor 16 and an intercooler exit gas temperature sensor 18 have been determined normal, whether an EGR cooler efficiency calculated is within a normal range is determined. When within the normal range, whether there is divergence between a calculation value of an intake temperature to be detected by an intake manifold gas temperature sensor 19 and an actual detection value of the sensor 19 is determined. When not in the normal range, whether the calculation value is excessively low is determined; and, just like the above, whether there is divergence between the calculation value and the actuation detection value of the intake manifold gas temperature sensor 19 is determined. Based on the determinations categorized, whether the EGR cooler 14, EGR gas temperature sensor 17 and intake manifold gas temperature sensor 19 are normal is determined.

主权项

1. A fault detection method comprising
providing, at a same position, two cooling water temperature sensors for temperature detection of cooling water entering into an EGR cooler and confirming that detection values of said cooling water temperature sensors are the same to thereby determine said cooling water temperature sensors to be normal; determining an intercooler exit gas temperature sensor to be normal when a detection value of the intercooler exit gas temperature sensor for temperature detection of intake air having passed through an intercooler is not excessively high during low load operation and is not excessively low during high load operation; using, as a precondition, a fact that the cooling water temperature sensor and the intercooler exit gas temperature sensor are determined to be normal; calculating an EGR cooler efficiency on the basis of a calculation value of an exhaust temperature at an entry of the EGR cooler calculated from a revolution frequency and a load of an engine, an actual detection value of an EGR gas temperature sensor for temperature detection of exhaust at an exit of the EGR cooler and the actual detection value of said cooling water temperature sensors; when said EGR cooler efficiency calculated is within a normal range, actually detecting a temperature of the intake air mixed with EGR gas and guided to an intake manifold by an intake manifold gas temperature sensor and calculating a temperature of the intake air to be detected by said intake manifold gas temperature sensor on the basis of a current EGR ratio, the actual detection value of the EGR gas temperature sensor and the actual detection value of the intercooler exit gas temperature sensor to thereby determine the intake manifold gas temperature sensor to be in characteristic fault if there is divergence between the calculation value and the actual detection value of the intake manifold gas temperature sensor and determine the EGR cooler, EGR gas temperature sensor and intake manifold gas temperature sensor to be normal if there is no divergence; and when the EGR cooler efficiency calculated is not within the normal range, determining whether said EGR cooler efficiency calculated is excessively low or not to thereby determine the EGR gas temperature sensor to be in characteristic fault if said EGR cooler efficiency calculated is not excessively low; and, if said EGR cooler efficiency calculated is excessively low, calculating the temperature of the intake air to be detected by said intake manifold gas temperature sensor just like the above to thereby determine the EGR gas temperature sensor to be in characteristic fault if there is divergence between the calculation value and the actual detection value of said intake manifold gas temperature sensor and determine the EGR gas temperature sensor and intake manifold gas temperature sensor to be normal and determine the EGR cooler to be in fault if there is no divergence.