constant cel fault code. - PeachParts Mercedes-Benz Forum

lsmalley · #1 01-17-2011, 06:00 AM

I am constantly getting a code 11 and sometimes a code 15, 18. even after resetting the code, the fault 11 will appear within minutes. if I just leave it on, a and go to reset it a few days later then one or the other codes show up. could it be my O2 sensor? right now my car has 271,000 miles on it and here are some things that could be related that I have done:
Bosch O2 sensor replaced. Done on 10/7/09 @ 246,939
Check air valve. Done on 10/9/09
Bosch H9DCO Spark plugs 6 total. Done on 10/6/09
*Bosch spark plug wire
set. Done on 10/6/09 @ 246,560
Air pump diverter valve replaced 10/23/10
*Overload Protection Relay replaced 7/9/10

Does anyone think I need a new O2 sensor? my car also cuts off on me while I'm driving.....not often, but its usually when I'm slowing down to a stop. not sure if there is any relation to the cel. and by the way, I do know what the cel code are, but I don't know how to correct them.

mbdoc · #2 01-17-2011, 08:30 AM

When the car is cold in the morning, does the air pump clutch engage & the pump run?

Have you checked the vacuum lines at the diverter & switch over valves?

lsmalley · #3 01-17-2011, 09:56 AM

yes, the vacuum lines are fine, I replaced them, and yes the smog pump engages. I'm at a complete loss

mbdoc · #4 01-17-2011, 10:25 AM

THAT car as well as most MB's does use the O2 sensor to monitor the air injection system. When the pump runs the O2 sensor must report that the system is pumping oxygen into the exhaust.

Have you tried operating the diverter valve with a hand vacuum pump. see if it holds vacuum or if the switch over valve provides vacuum?

lsmalley · #5 01-17-2011, 03:24 PM

I have not tried the prcedures that you mentioned above, as i do not know how, nor do i have the necessary equipment or tools. i did disconnect the vacuum line to the diverter and got suction and i also had the diverter off and was able to check it and it seemed to work fine.....but then again who knows. the O2 was replaced about 25,000 + or - miles ago....thats the only thing that i can think of. i have meticulous record keeping for my car since 2005 for all servicing and replacement parts and can't see what else could be causing it. last time i had a code 11 on the car it was the check air valve, which was replaced less than a year ago, and i did check that and it is fine.......smog testing is still 6 months away, but just wanna get this under control

lsmalley · #6 01-22-2011, 03:43 AM

Ok, so my check engine light was constantly on giving me the air injection fault code 11. I bought a check air valve and replaced and the problem was fixed. I guess I decided to swap out all my vacuum lines one day and then my CEL light came on again giving me the Air injection code again. I was trying everything to fix it for months and months. I bought a new air diverter, I seafoamed the hell out of my car, and I was just about to buy a new O2 sensor (not cheap) until I decided: "let me go out and give it one more look before I spend money on a 15 month new O2 sensor that was replaced in October 2009." I reset the light, checked all the vac lines, took off the diverter, checked the smog pump, and everything was good. Turned the car on and let it run and WALLAH! the light comes on again. Stumped, I decided to look at the picture of my engine that I took when I first had the CEL code and cleared it with the check air valve.(I always take pictures of everything under the hood before I replace anything)....Then it hit me: in the picture my ca valve is black on the top, white on the bottom.....as I stand there, I realize my mistakie, I took off the check air valve and flipped it around, reset the code and drove the damn car for an hour and no light! I had the check air valve on upside and didn't even realize it!

Moral of the story......the simplest answer can be used to solve a complicated problem