Abstract: A fluid level measurement system using a buoyant body includes a guide part installed in a direction perpendicular to the bottom surface of a fluid storage tank, and provided with a space in which a fluid can move therein; a buoyant body inserted into the guide part, and configured to float along the surface of the fluid inside the guide part; and a measurement part coupled to the top end of the guide part, and configured to measure the level of the surface of the fluid inside the fluid storage tank by transmitting a signal toward the buoyant body in the inner space of the guide part and then receiving a signal reflected from the buoyant body.

Abstract: A fault diagnosis method of an exhaust gas post-processing system may include a detection step detecting any one or more of an operating state of a lean NOx trap or a state of an urea tank, a determination step determining whether the state of the lean NOx trap or the urea tank detected at the detection step satisfies a corresponding condition to block monitoring of a purification efficiency of the exhaust gas post-processing system, and a blocking step blocking the monitoring of the purification efficiency of the exhaust gas post-processing system when the state of the lean NOx trap or the urea tank at the determination step satisfies the corresponding condition to block the monitoring of the purification efficiency of the exhaust gas post-processing system.

Abstract: A fault diagnosis method of an exhaust gas post-processing system may include a detection step detecting any one or more of an operating state of a lean NOx trap or a state of an urea tank, a determination step determining whether the state of the lean NOx trap or the urea tank detected at the detection step satisfies a corresponding condition to block monitoring of a purification efficiency of the exhaust gas post-processing system, and a blocking step blocking the monitoring of the purification efficiency of the exhaust gas post-processing system when the state of the lean NOx trap or the urea tank at the determination step satisfies the corresponding condition to block the monitoring of the purification efficiency of the exhaust gas post-processing system.

Abstract: An exhaust gas treatment system includes: confirming that an engine stops operation; sensing present pressure difference between front and rear sides of an EGR value; setting learning value by performing large offset learning, if the present pressure difference exceeds an absolute value of a first lower or upper values; setting learning value by performing step learning, if the present pressure difference exists between first and second lower values that is larger than the first lower value or the present pressure difference a between first and second upper values that is smaller than the first upper value; and setting the present pressure difference value as a learning value, if the present pressure difference exists between the second lower and second upper values. The exhaust gas treatment method accurately learns the pressure difference of the EGR system to improve the quality of the exhaust gas and securely control the EGR system.