Folks - I looking for a little help. I have been getting CEL for the EGR P0402 for excessive recir. I removed the EGR, EGR pipe and cleaned them with carb cleaner, and reset the code. Started the car and drove for about 20 miles, no CEL. On the very next start, CEL came on and it was the same code - P0402.

Question: which component sets this code? Is it the EGR or a sensor in the system? Is there a way to test the EGR? Is this code related to the EGR failing to close all the way? What is the component next the EGR that looks like a temp sensor? (screws into the same exhaust duct as the EGR)

The EGR is easy to replace but I don't know the system well enough to say that the problem is the EGR and not something else. I appreciate any help or advice you can give. I think this must be an easy problem to solve.

2008 E320 bluetec, 110,000 miles.

I am not familiar with the diesel systems, but according to what I've read about EGRs generally and P0402, is that the EGR valve is allowing too much exhaust gas to flow into the intake manifold. Given the text of the error message, that will come as no surprise to you.

Likely causes for that include a bad vacuum hose, if it is a vacuum-actuated EGR, or a dirty or worn EGR valve. For excessive flow to be the problem, I doubt that other passages in the system are blocked, because that would cause a lack of flow, not too much flow, I suppose.

Disassembling the EGR and cleaning it can help and check movement of the pintle and diaphragm, along with cleaning the port it fits into, but you shouldn't spray solvents on the diaphragm (so your carb cleaner may not necessarily have been the best thing to do.)

I can't say much more than that.

Haynes' "OBD-II & Electronic Engine Management Systems" book, ISBN 1 56392 612 1, is a good reference for more detail. Your local parts store probably has a copy for about US$20

Does anyone know if the EGR valve is touching off the code or is there a sensor that trips it?

Can I test the proper operation of the EGR valve?
My system is electronic - no vacuum hoses.

I wanted to post this as a follow up...My EGR has given up the ghost. Over a year ago, I took the EGR off and clean it and the tube, and tube connections and replaced with new gaskets. It worked like a champ until this month. Started getting CEL for EGR. I have the dealership check it for me and they found coded 2355-001 for EGR malfunction. They performed guided test through ads and found out EGR is defective and needs to be replaced.

The cleaning helped me get over a year out of it but now needs to be replaced. I'm going to replace it myself since it is pretty straight forward and on top of the engine.

2008 E320 Bluetec
130,000 miles - runs like a champ!

Did you get around to replacing the EGR valve and did it solve the code issue?