The EGR system is applied only for the four-cylinder cars from 1999 to 2005, where, through the EGR valve, the part of the exhaust gases gets to the intake manifold to decrease the combustion temperature and, thusly, the emission of nitrogen oxides. These are the EGR valve, EGR vacuum solenoid valve, manifold absolute pressure (MAP) sensor, the powertrain control module (PCM), vacuum hoses and wires; the position of the EGR valve is controlled by vacuum through the EGR vacuum solenoid valve through signal from the PCM, while the MAP sensor supplies sufficient information for EGR functioning. To perform replacement on an EGR valve, first, remove the engine cover to do this, remove the vacuum hose, and remove the bolts holding the valve in order to lift it up; check for excessive stick and if there is a lot of dark black Karbon deposit then it is advisable to replace. Turn the supply air vacuum control solenoid valve near the valve cover counter clockwise and remove it together with the vacuum harness and a couple of hoses you may label if necessary and the bolts. The class installation process is the reverse of this for both of the components. The MAP sensor is situated at the rear side of the intake manifold, and its function is to provide information to the PCM only and it doesn't control the common engine operations; to remove this component, the wiring harness and vacuum connections need to be disconnected, and then the unit can be unbolted, while the installation process requires the reversed steps.