EGR Flow issue P0400 01 ML430 - PeachParts Mercedes-Benz Forum

JimmyL · #1 03-03-2013, 09:55 PM

Love those "Check Engine" lights!!!!

Been doing a bit of reading and searching on these EGR issues (P0400).
Purchased the ML from a supremely respected forum member. Check engine light situation was fully disclosed.
EGR tube had been cleaned.
EGR replaced. (I'm guessing new)
Vac lines replaced. (I guess some in back?)

Code would throw usually coasting down from hwy speed say on an exit ramp. It fires more frequently now, with around town driving. No secondary codes.

So today, I dove in.....

Drained and removed overflow tank.

Pulled air filter box lid, MAF assy, and intake ducting to get to the hardly accessible business end. The firewall end......

You can see the EGR tube above. (shiny with a wrinkle section)

I went ahead and pulled it out just to check. Had to be sure it was clean. It was very clean!

Put it all back together. No vac lines in back were undone, before or after.
John H gave me some very good info on Facebook!!
Here is one thing I found up front. First, there is some kind of air pump that I know nothing about!! Lots of vac lines, plumbing, a couple of valves of some kind, and a couple of other components that I haven't as of yet identified.

I did find a vac line to/from the driver's side valve had a hole in it. So I replaced the vac line to this valve.

JimmyL · #2 03-03-2013, 09:55 PM

The vac lines at the other valve seemed fine. Plumbed differently. And also going into something I can't identify. Also, there is a small blue check valve (maybe) coming from said mystery assembly? (passenger side)

And this lives back by the brake booster. One line goes down towards EGR stuff, the other I can't remember. Maybe brake booster.

On FB John said to squeeze off the thick hose to the two valves up front, one at a time of course, and listen for the engine pitch. If the pitch doesn't get higher then that side is blocked or valve not opening.
Does it open via the small vacuum line? They did both hold vacuum.
And is there any way to know the air pump is operating? I guess remove something while it's running?

I've got some more testing to do with this ML based on info above. Any other light that can be shed on this EGR system would certainly be appreciated.....

JimmyL · #3 03-09-2013, 12:05 PM

Light stayed off for a day! NOT two.......

Skid Row Joe · #4 03-09-2013, 11:24 PM

Jimmy,
No help here, but as I understand it, you can't get it Texas safety inspected while the Check Engine light is on....(ask me how I know.....

).

The late David S. Poole was my indy of choice, and frankly, I have a trust issue as far as anyone I don't know working on my MB. I'm just not qualified to delve into diagnosing/fixing, w/o making a basket case of it, so, I try to learn or pick up what I can about tech procedures on Peach Parts.....

David shared a building and shop space with another general automotive indy that did my Texas inspection the last two years, if you're looking for a inspection shop? Since David worked on my MB in April 2011 dousing the Check Engine light by replacing something that went out in Flagstaff, AZ. on the way back from Las Vegas in the old diesel. Unfortunately, there are a couple three things that were needing to be done on the diesel, but I waited too long in getting it back to David.

I like the earlier 2000s MLs, in the V6 version, so I've been following the thread.

TylerH860 · #5 03-12-2013, 01:15 PM

With the code scanner I gave him he should be able to clear the codes and pass a safety inspection. Still hopes he gets it sorted out. Thankfully Kansas does not have these inspections, and after throwing several hundred dollars at a useless silly thing, I drove on.

JimmyL · #6 03-12-2013, 11:34 PM

You're right Joe, a check engine light is a no-go for inspections.
I keep clearing the code, and hopefully we can drive this thing for several days in a row without the light coming on. Then I can hopefully get it inspected, then have a year to figure this silly thing out.

Whiskeydan · #7 03-14-2013, 11:58 AM

Black tape?

JimmyL · #8 03-15-2013, 01:05 AM

Quote:

Originally Posted by Whiskeydan

Black tape?

Don't forget grasshoppa, I still have the extension and socket that fit the indention in your forehead!!!!

JimmyL · #9 03-19-2013, 10:18 PM

Well, finally got the ML inspected today!!
I cleared out the code, and then had about 3-4 days of driving and then letting it cool down. Cycles. Included some hwy time.
Went in this morning and..... FAIL!!!!

3 sensors weren't ready.
I hadn't gone enough miles. Dang!
Well, I had a service call in Ft Worth, so that was going to be a hunnert mile round trip. Excellent. I just had to be very careful that I slowed down gradually from highway speed, and I guess high EGR vacuum. Coasting off the fwy is what will fire the code off.
So, made it back 103 miles later, and it passed just fine!!
Now I have another year to figure it out!