Check engine error codes P0170 and P0173

A common issue on Mercedes that set those codes is a defective Mass Airflow Sensor. You would need to connect a scan tool and look at the airflow the MAF is reporting to make sure. At idle you should see between 3.5 - 4.5 grams per second and between 8 and 12 g/s at 2500 no load rpm. Be careful of the lower cost replacements, very often they are out of spec as well.

Mercedes is one of the few companies that use those codes. They show that the ECM is pushing the fuel trim controls over the range they are supposed to operate in. They use a very narrow range compared to other makes. You may not notice the minor change in mileage they cause or other minute changes. However the computer sees them and sets those codes. The only real way to find the problem is to watch the numbers live.

Hey JACKDOIT,

My wife has this car and I just went through a whole ordeal with a code that involved the intake camshaft problem, the bottom line is the car had a boot between the mass air flow sensor and the blower which I replaced. The codes kept coming up, I finally figured out that the adaptation of the computer needed to be cleared so the computer could "relearn" the engine again, have not had a problem since.

This cannot be done with a normal scanner and must be done with the mercedes tool with the appropriate program.

Please let us know happens so it will help others.

Best, Ken

Yep, if the MAF is not reading correctly it will cause problems but may not be enough to trigger a check engine light.

I wish you were close I have one right here you could try :)

Let us know.

Best, Ken

Nice work Jack! Glad you could get the problem fixed. Please use 2Carpros anytime we are here to help and tell a friend!

Happy Holidays!