1998 E300 Code P0243 Solved! - PeachParts Mercedes-Benz Forum

DavidLearner · #1 03-23-2010, 04:12 PM

The people and information on this forum have been tremendously helpful to me, and I wanted to contribute this to help somebody avoid a bit of aggravation and expense. Here is how I got rid of my (stubborn!!!) P0243 code:

The car is a 1998 E300 Turbodiesel with 199,xxx miles. It started setting P0243 codes some months ago. I took the following steps to find the source of this code. I changed only one thing at a time and then tested to see if that cured the problem. It has been a rather long, drawn out affair!

Exchanged the turbo wastegate transducer and EGR transducer;
Checked vacuum source at turbo wastegate transducer (27” Hg);
Replaced vacuum hose from transducer to wastegate diaphragm;
Verified wastegate diaphragm integrity and action with Mighty-Vac pump;
Checked wastegate vacuum levels per Mercedes specs (Thanks, Terry Allison!);
Tested transducer vent filter with Mighty-Vac found no restriction;
Disconnected vent filter hose just to be sure;
Banged head on wall;
Checked all metal and rubber air piping from turbo to intake;
Replaced rubber hose to MAP sensor;
Added hose clamps to MAP sensor hose;
Verified MAP sensor intake hose nipple open and clean;
Graphed MAP sensor voltage vs pressure (vacuum and boost) – it was linear;
Banged head on wall;
Cleaned MAF sensor;
Replaced engine air filter;
R&R Intake manifold to replace large o-ring seal;
Pulled K40 relay board, re-soldered, re-installed;
Bypassed wastegate transducer – hooked vacuum source directly to wastegate diaphragm.

NONE of the above had any effect – the car just kept throwing the code and going into “limp mode”.

Monday, I took the car to an excellent muffler shop and asked them to check for an exhaust restriction. He drilled a 1/8” hole in front of the catalytic converter and attached a pressure gauge. One throttle blip told the whole story – the converter was stopped up. After repairing that problem, the code is gone and the power is all back!

Since I never saw any mention of an exhaust problem reference P0243, I hope that this information will help somebody. It was not at all obvious to me that a clogged converter could throw a P0243 code!

KarTek · #2 03-23-2010, 07:12 PM

Great job! Way to stick with it!

jessejames4 · #3 07-09-2010, 02:14 PM

Dude, you're more stubborn than I am and that's saying a lot. Did the guy figure out what was plugging it up? Excellent drill down to the fix! You should get a medal.

willy2004 · #4 08-10-2010, 01:24 AM

wow, clogged converter?!
who woulda thunk it!

I've been researching this problem and that's the first i've heard of this
anyway, nice work.

engatwork · #5 03-13-2012, 06:28 PM

The car has been on a steady diet of homemade 100% biod since '09. The guy at the exh shop said that the pluggage was as bad as he had ever seen (I did not get a chance to see it). Seems that when the fuel is not quite up to spec it can plug a converter.