EGR stands for Exhaust Gas Recirculation, I know recirculation isn't a word in the dictionary, however it's an automotive term that describes what is happening. The way the system works is when the car is driving down the road, under load and the conditions are correct, the Engine Control Module will direct the EGR controller to open allowing vacuum to open the EGR valve just under the Throttle body allowing exhaust gas to be induced into the intake. This exhaust gas although dirty will help to cool the mixture in the cylinder and cut down on emissions, especially Nox. The most common codes that are set for a problem in the EGR system are; 154 EGR system flow too high, 413 EGR temperature sensor signal missing, 235 EGR controller signal missing, and 241 EGR system flow too low. The biggest problem with the EGR system is that in time, usually after 60K miles the hole in the manifold gets clogged up and causes codes to be set. The below pictures and writings are to help you remove the EGR valve and clean it up.
I'll start with the air box and hose from the air box to the throttle body removed. Parts that you will need are a new throttle body gasket, a new EGR valve gasket, flame trap, a good carb cleaner. While everything is apart make sure all the rubber elbows and lines are in good condition, if not replace them. The EGR temperature sensor wire connector is hidden under the dipstick tube and is a not easy to work out to unplug. I remove the Idle Air Motor just to get things out of the way, you could leave it there. The throttle body has to be removed, four 10mm bolts hold it in place. The lever from the throttle pulley to the throttle body is snapped on like a ball and socket. There is also an electrical connection to the Throttle position sensor that has to be unplugged. There are two vacuum lines that are connected to the bottom of the throttle body, disconnect them.
Once the Throttle body is off you have access to remove the EGR valve assembly. Loosen the 22mm nut first, this holds the pipe from the exhaust to the inlet of the EGR valve in place. Once you have the 22mm loose, you might want to smack the line with something to ensure it is broke loose from the EGR valve. Once the 22mm is loose I follow the temp sensor wire down to the dipstick tube and work the connector out from under the tube and disconnect it. The 8mm bolts are all that holds the EGR valve to the valve body, the one you can see in the pictures is easy to take off, do it last. The one hidden out of site inboard is a hard one to reach, I use a ¼ inch ratchet and medium socket to break them loose and then if I'm luck they can be worked out with my fingers.
After the 8mm bolts are off the only thing left connected to the EGR valve is the vacuum line from the controller. This picture shows the Idle Air Motor removed. The EGR valve has a vacuum bellows/diaphragm that has a vacuum line attached to it. Slide the clip on the hose up a bit and then disconnect the vacuum line as well as the two that are attached to the vacuum tower. Move all the plastic vacuum lines gently as they get hard and brittle with age. The vacuum lines attach to the controller under the plastic cover on top of the radiator fan. When you put everything back together make sure both ends of the vacuum lines are connected good. With the EGR valve out of the car, use a 14mm to take the temp sensor off the valve. Clean the temp sensor with a wire brush to get all the carbon off the sensor. Use the carb cleaner to clean the inside of the valve out, I have a wire brush on a drill that I use to clean out the openings on the EGR valve. Notice two pictures up that white arrow is pointing to the hole on the bottom of the intake manifold. This hole is normally totally clogged up with carbon and gue. Make sure that hole is cleaned out all the way before putting the EGR valve back on. Also Clean the throttle body before attaching it back to the manifold. When I have the EGR valve off the car I use a hand vacuum pump to operate the valve and watch it move inside the valve just to make sure that is working. Going back together it is hard to hold the EGR valve in place with the gasket so you can start the 8mm bolts. The 22mm nut/pipe makes it a bit hard, I don't know of any trick here but sometimes you might need someone else to pry the pipe back a bit so you can get the 8mm bolts started.