How to Repair/Clean the EGR on a 5.7 Hemi

I had the P0406 DTC which is one of several related codes - EGR Signal too high. There are several EGR codes that are related to the fact that the EGR valve cannot respond fast enough for the PCM to be satisfied that it is working right. The code came in at 8:30 pm so I worked on "repairing" the EGR till 10 pm. This is a week later and so far, so good. I cleared the check engine light with a scanner. This EGR is a robust design and really shouldn't have this kind of problem - ever! ( see next)
THE mechanical problem - The design of the EGR allows the exhaust gases to put "pressure " on the seal that should keep them from laying down carbon deposits on the stem of the valve. Eventually though, the stem carbons up with laydown from the exhaust gasses dragging the EGR's action till it will not do what the PCM tells it to do.
THE Repair - I wish I had pictures because anyone with a modest amount of mechanical talent and a desire to spend their money on TOYS instead of EGR valves can do this. First, unplug the electrical connector on top. If you have a meter, measure the resistance across the lower two prongs inside the electrical connector. There should be a very low resistance reading: 5-15 ohms. it's hard to reach/see but you can do this before you remove the EGR from the truck. This reading checks the health of the coil that activates the EGR. If it reads an open circuit (not likely) or O ohms (shorted out), the EGR will need replacement, stop here and go to the auto parts. If the reading is good proceed with the rest of the repair (if you're so inclined). This part is for the more mechanical folks. Unbolt the EGR valve. There are 2 bolts with 8 mm heads to hold the tube flange. There are 2 10 mm bolts that mount the EGR to the engine.
The coil is held in the coil housing by 6 prongs that need to be carefully pried back so the coil can be withdrawn. Note: there is an o-ring (red-orange) in a groove near the top shoulder of the coil. Mark the position of the direction the electrical connector is facing before pulling the coil out for later reassembly. Inside the coil housing, you'll see the plunger that responds to the coil when it is energized. At this point you could "exercise" the plunger by forcing it up and down to breakup the carbon laydown on the stem and then reassemble it. This would only get you part of the way. There is a stamped "washer" at the bottom of the coil housing that needs to come out. The washer creates a double bottom with the the lower fixed coil housing bottom. There is a small air space in between. If you look in through the openings around the lower part of the EGR you will see a small wire sticking through. When you take out the washer, be sure to keep track if this wire so you can reinstall it. With the coil out and the washer out, use a small bladed, fine screwdriver (like a jeweller's screwdriver)and carefully remove the red-orange o-ring at the bottom of the coil housing. If this o-ring comes in contact with any kind of cleaner, it will swell and won't fit back in later. Set it aside for later re-installation. Use a spray cleaner like brake cleaner with a nozzle tube. Spray it down in the spring assembly where the plunger attaches to the valve and passes through the coil housing. "Exercise" the whole assembly by moving it up and down and rotating the assembly to loosen and remove the carbon laydown on the stem. Turn the whole thing over and tap the side of the coil housing so the harder flakes of carbon that didn't dissolve will fall out of the housing. Repeat until the plunger/valve assembly moves freely. When the brake cleaner is evaporated and everything is dry and free of carbon laydown proceed to lubricate the valve stem. You should lube it with a graphite spray lube to keep it moving free and resist the exhaust gas temperatures. Some lower temperature lubes might gum up your repair and bring back the code(s). Using a spray nozzle to direct the spray, lube the spring area where the stem passes through the housing. Again exercise it up and down to be sure it moves freely. reinstall the wire pin, reinstall the o-ring at the bottom, re-install the stamped washer and reinsert the coil being sure your electrical connector is aimed where you marked it. Be sure the shoulder of the coil is all the way down against the coil housing, don't cut the o-ring near the top when you re-install the coil. Bend the tabs back in place. Bolt it all back on the engine with new gaskets. Reconnect the electrical connector, clear your "Check Engine" light, test drive.
I did this repair for my own sake. I cannot make a guarantee of your results or the long term effectiveness of this repair having only done this a week ago but it woke my engine up.