CRD - Bad EGR Air Flow Control Valve and Chaffed Turbo Hoses

T^2 · **Posted:** Sat Jan 28, 2006 10:16 pm

I had the EGR valve replaced for a second time a couple of weeks ago. Unlike the first time, the only DTC code I got this time was P0401. The previous time I got codes, P0401 and P0299. The CEL came back on the day after the EGR was replaced. Once again it was DTC P0401. So, I took the vehicle back to the dealer.

The duct from the air box and the turbo-to-intercooler hose was found to be rubbing (where the hose and duct go into the turbo) together and the turbo-to-intercooler hose chaffed through causing a leak. They ordered and replaced the duct and hose but found that the DTC code was still present. After further troubleshooting and consulting with tech support, the EGR Air Flow Control Valve was found to be stuck open.

The EGR Air Flow Control Valve - what was that? I hadn't heard of it until the mechanic told me about it. So, I asked him what purpose it served. Apparently under certain conditions there is insufficient EGR flow (even with the EGR valve completely open) and air flow from the turbo has to be limited (via this valve) to increase the ratio of exhaust gas to air. If this valve is stuck open the system will detect the insufficient EGR flow and produce the code P0401.

From what I gather, this EGR Air Flow Control Valve resides somewhere between the intercooler and the intake. The mechanic told me that this valve is unique to the VM CRD and not found on the CTD or the Sprinter's Mercedes diesels. So, does anybody know more specifics about this valve?

The mechanic told me that he replaced the EGR Air Flow Control Valve but not the EGR valve itself (after all it was just replaced and unlikely to be malfunctioning). The part numbers and descriptions of the replaced parts (for the Air Flow Control Valve) are as follows:

Part # Description
---------------------------------
5142799-AA Valve EGR 14033001
5142806-AA T/Body EG 14033001
5142613-AA Gasket EG 9001004

Anyway, I want to pass on my experience with this incase this info may be helpful to anybody experiencing similar issues. I'd also like to hear any amplifying or clarifying information or opinions that you all may have about this issue.

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

Sounds like the air valve in the intake tube, which is the aluminum tube the intercooler hose connects to. It also functions as an anti-shudder valve when the engine is turned off. When the EGR is cycled on, this valve is also used to decrease fresh air flow by closing slightly, which creates more pull on the EGR supply line. From what I've been able to figure out by reading, when the ECM commands EGR on, it can also activate this valve, then monitor the MAF for the corresponding reduction in fresh air flow. The designers were pretty determined to get that exhaust gas back into the engine, or they couldn't pass the NOx reduction emissions requirements. Lots of design effort went into this.

CRD - Bad EGR Air Flow Control Valve and Chaffed Turbo Hoses

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