New EGR, checked vacuum hoses, P0400 remains!!!
Thread Starter
Newbie
Joined: Jul 2019
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From: New England
E430, C320(2004)
New EGR, checked vacuum hoses, P0400 remains!!!
2004 C320 getting P0400 code and car is surging after shifting, primarily from 1st to 2nd gears. Idle is sometimes erratic after engine is up to temp. I changed EGR valve and checked the vacuum hoses for leaks. I was unable to remove the EGR valve SS tube to check for a blockage but the valve was free of any carbon build up. If someone has a suggestion on the EGR tube removal it would be appreciated. I checked for voltage to the EGR - good. EGR Valve is clicking when voltage is applied. What would you suggest I try next? This is making me nuts
Thread Starter
Newbie
Joined: Jul 2019
Posts: 11
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From: New England
E430, C320(2004)
Russell, here in the US in some states our vehicles must pass a safety and environmental check. Our politicians have decided that even though China can start up new coal-fired power plants at the rate of one a day we cannot have gasoline or diesel powered vehicles that would release a whisper of NO2 into the atmosphere. CEL lights illuminated for any emission fault is taboo. Blanking an EGR valve results in a lit CEL. But thanks for the reply
Thread Starter
Newbie
Joined: Jul 2019
Posts: 11
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From: New England
E430, C320(2004)
Sorry I haven't gotten back to you Russell. EGR valve issue has been resolved. However, in order to pass emissions test a number of data points must be reported to the ECU ( I think 6 points out of 8). I currently have 4 that are reported completed. Today a "comm link failure" pending code appeared. Not sure I understand the "pending" and why it doesn't become a normal code. At any rate car is still operating poorly and I have no idea where to start.
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Senior Member
Joined: Dec 2008
Posts: 378
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2015 S550, 2017 GLS450
My code didn’t clear for a week but eventually the CEL went off. I answered too early as it is highly recommended to replace all the tubing with the EGR valve. The metal tube is not easy to remove and can only be removed with the valve removed first. Mine was full of gunk, but the smaller rubber vacuum hose from the EGR valve was completely shredded and rotten after 140K miles. I don’t know if any other common problems that will throw the P0400 code. It’s the valve or tubing.
And while you’re back there behind the engine, it’s a great excuse to clean the MAF sensor, the throttle body, and replace the crankshaft sensor… all maintenance issues on higher mileage cars.
Did you run an OBD2 scan with a factory-level scanner?
And while you’re back there behind the engine, it’s a great excuse to clean the MAF sensor, the throttle body, and replace the crankshaft sensor… all maintenance issues on higher mileage cars.
Did you run an OBD2 scan with a factory-level scanner?
Last edited by bkdc; Jan 3, 2022 at 08:24 PM.
Senior Member
Joined: Dec 2008
Posts: 378
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2015 S550, 2017 GLS450
One thought came to me with the shifting issue. A common failure in the 5 speed Mercedes transmission at higher mileage is failure of the transmission circuit board. Porsches, Jaguars, and the many Benz cars using the transmission get this issue and it’s a pretty straight forward swap out. If idling is bad and you’re not getting CELs, I’d check your throttle body and get it cleaned. You need to remove the MAF sensor to get to the throttle body.
Last edited by bkdc; Jan 4, 2022 at 01:06 PM.
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W203
2004 C320 getting P0400 code and car is surging after shifting, primarily from 1st to 2nd gears. Idle is sometimes erratic after engine is up to temp. I changed EGR valve and checked the vacuum hoses for leaks. I was unable to remove the EGR valve SS tube to check for a blockage but the valve was free of any carbon build up. If someone has a suggestion on the EGR tube removal it would be appreciated. I checked for voltage to the EGR - good. EGR Valve is clicking when voltage is applied. What would you suggest I try next? This is making me nuts
can anyone help with the name of the rubber horse circled up top it has a few holes in it and my fuel economy has shot up
