Fixed p400 & p200 codes, on '97 E 300 D

[nelbur]

This is a NA diesel with the intake flapper valve near the EGR. Both codes set at the same time. The p400 is an EGR flow insufficient code, while the p200 is mysterious on a diesel. A search indicated that bad vacuum hoses could set it.

I went over the vacuum hoses on the EGR and the cross over pipe valve, and erased the codes, only to have them come back at idle after the engine warmed up. I have seen the flapper valve on the intake operate at idle in my driveway when I was working on a running engine, so I knew that the EGR check was possibly involved in the code set. I checked the vacuum at the hard vacuum line that connects to the top of the vacuum transducers that work the EGR and flapper valve, using the gauge on my mity-vac, and found only 5 in of Hg. I also found that it took nearly 10 in. to open the EGR, so I knew I had found the problem.

Since the power brakes worked fine, I assumed the problem was a leak somewhere after the brake booster. I disconnected the hard line that goes from the booster to the passenger side, and blew on it. I could hear a slight hiss near the firewall, but the line was not visible. After about an hour of removing the wipers and many cowl pieces I was able to extract the line, but found it to be in good shape up to where it went under the electronics box on the passenger side. Now that I could blow on it while standing on the passenger side, I could hear that the hiss was under the electronics box. I could see a line going through the firewall, so I hooked it and teased the lines up between the fender and the box. I found a very fragile looking plastic T. It looked intact but blowing on the line revealed that one arm was cracked. I broke all three arms off and connected a new T using three 6" piecesof vacuum line to alow rerouting the line so it was not under tension, and easier to access. That solved the problem and the codes have not come back after a few weeks of driving.

While this car has a uncommon EGR test proceedure, most newer 210 diesels will likely have the problem T in the vacuum line and should set codes if the EGR function is checked by the computer.