They say that 98% of the time, these codes indicate a faulty EGR valve.
As you can see in the picture I dismantled my valve and found this obvious problem. This part inside, maybe a resistor, a diode or what else, is connected to both pins of the solenoid. The solenoid and the rest of the valve seem to work fine.
If I could find out what is this burn (or broken) part, I would replace it in the hope that it solve my problem. Otherwise, the price of this valve is 178$ plus tax at the dealer.
My guess would be the burnt item is a diode, for back-emf suppression. It would be a reverse-biased diode with a current-rating > the solenoid peak current.
Yes, It really look like a diode. This compare to a diode that I have in my part box. The diode number from my box is is 315-6GI818 but I don't find any reference for it.
The solenoid resistance is 8 Ohms. Would you have a part number that I could try?
Changing the diode with the one that I had got rid of the P0404 for a few days but it came back. The P0406 came back right away.
I will order a new EGR valve from rockauto.com along with other parts. The price is really very good compare to the best price that I found locally (125$).
For a total of 115$ CAD this, as I asked them, including shipping, taxes and everything else I will get the better valve plus a set of Champion 7440 spark plugs.
The shipping to Canada is more expensive I suppose in part because of the duty fees.
BTW if ever you have a 2006 Caravan, there is a hard way and an easy way to remove the valve from the motor. Here is the easy way.