I just purchased my first Mercedes ('00 ML320) from the original owner, drove approximately 100 miles of the 130 mile trip home and stopped at the grocery store when the Check Engine light came on in the parking. I had the code read the next day (P0170) and had the light turned off, thinking it could possibly have something to do with going from sea level to 5K ft. in altitude. The light came on again within 5-10 miles, at which time I researched the codes and ordered new 02 sensors and replaced both on the left cylinder bank.

The car has been running fine the entire time the light has been on. However, about a week ago, I just jumped in about mid-day and took off to do a quick errand without warming it up as I usually do. There was an obvious misfire upon acceleration for approximately one mile, upon which time I pulled over and stopped and restarted the vehicle, which cleared up the problem. It has done it one more time under similar circumstances since.

I had the codes read at my local Auto Zone today: P0170, P0173, P0300; P0302; P0306 (the latter three being the obvious misfires registered). Before throwing more parts at this vehicle (MAF sensor would be my next step), does anyone have any insights as to what I might have going on? I was told by the previous owner that this vehicle has always been dealer maintained, which was substantiated by the CarFAX report that I ran prior to purchase. However, my husband was a Jeep mechanic for 20 years and can easily perform any repairs, but is unsure of European diagnosis.

 

I'm having exactly the same problem... P0170 and P0173 but the car runs fine. Had the fuel filter and integrated fuel regulator replaced.... things ran well for about 500 miles before the Check Engine light triggered again.

Did you ever get yours fixed? If so, how?

 

Yes, I was wable to fix it by replacing the MAF sensor. We had removed and cleaned the sensor on two occasions, which did not work. Utlimately, I just broke down and bought a new MAF off of eBay for a total of $156.00 (including shipping), and in less than 100 miles of driving the vehicle, the CEL went off on its own and I have had no further problems. This site gave me a ton of help in diagnosing and replacing the sensor, which just fits inside of the plastic housing behind the air filter/intake (I did not replace the entire housing, just the sensor). LOL.

 

i changed my mass air flow sensor and the light still remians