Well, I have the P0405 code active on my 06 6.0.
I removed it and cleaned it. I have about 130k on the truck and never had to do anything internally to the engine.(knock on wood) I do run Hot Shot secret in the oil. The EGR valve was partially sooted up, but it did not seem as bad as some that I have seen online.
I checked the resistance of the various pins.
Pins B and C: 50-2,500 ohms
Pins C and D: 2,000-7,000 ohms
Pins B and D: 3,000-7,000 ohms
and all 3 readings where in spec, but the code is still active. I also vacuumed out the hole in the intake before I re-installed it.
So far, the only symptoms I can say that I see is at highway speeds, when the engine/trans downshifts on inclines, it seems to bog down a little more and puts out more black smoke than before. Other than that, I see nothing different when driving it.
So, is there anything else I can check before I get a new EGR valve?
Any brand of valve better/worse than others?
What problems will happen if I don't install the EGR valve and fix the code?