Mr. CDI

Have a 2008 320 CDI that has a check engine light problem that hasn't been resolved. Been to dealer 10,000 miles ago to check this. They replaced fuel filter, air filter and supposedly reset system. After driving, CEL came on again. They CEL goes out after 100 - 200 miles but often comes on again sometime after filling with diesel. Just had the vehicle in for 40K service to have them check it again they said multiple 02 sensor precat codes (02 upstream open circuit, 02 thrust value below limit, part load fault value below limit 02). They rest Lambda values suspecting this wasn't done when the air filter was replaced previously. After driving for a day or two, CEL comes on again.

Now I am wondering if the biodiesel in Oregon has anything to do with this. In Oregon, the law requires gas stations to pump biodiesel, not sure if its B15 or not. I live in the Portland area, any other diesel owners have this problem?

Max Blast

MB only certifies their engines to be compatible with B5, no more. If it in fact is B15 it may have something to do with your CEL. Biodiesel has most of the chemical properties of fossil diesel oil, but some others as well such as being harsher on fuel system parts and requiring filter changes as closer intervals. Did they run a test on the 02 sensors? It is possible that your pre-cat 02 sensor is failing and that the codes it is throwing don't have anything to do with the fuel you are using.
I also don't see why they would have to reset lambda values after changing an air filter. The car reads the resistance in flow across the filters and should adapt on its own.

BTW Oregon law only forbids you from pumping your own gasoline, not diesel. You are therefore free to assure the quality of the fuel you put in your own car.

lkchris

Mercedes dealers have been provided by MBUSA with VERY sophisticated means to determine whether biodiesel > B5 has been used.

Mr. CDI

I did fill up this morning, I was mistaken about the biodiesel rating. The pumps state B5 S15, so the max is 5%. The Union 76 was out so I filled up at the Shell station. In regards to testing the O2 sensors the dealer did and tested O.K. Drove to Lincoln City this morning but the light never went out. Engine runs fine, I re-set the MPG computer around McMinville and drove about 60 miles between 50 - 65 mph and got 30 MPG when I arrived. Impressive fuel mileage, although the latter part of the trip was slightly downhill to the coast.

Its puzzling, I've been living with this for awhile but I'm nervous if something else goes wrong to trigger the CEL I won't notice because its already on.

Fourdiesel

B5 is OK per Mercedes. More is not. It turns out that the ability of biodiesel to not change physical properties (viscosity, 'gummyness' etc) at the high pressures and temperatures inside common rail diesel injections is poorer than it is for dinodiesel. In other words, it just isn't as stable at those pressures and temperatures.

REQUIRE the dealer to cure the CEL!

Brocktoon

The truth is that the engine can handle way more than B5. You can hear it from Benz (DC) and Bosch officials in the vids you can see in this thread:

https://mbworld.org/forums/gl-class-...e-answers.html