error code P0170, P0173?

P0170 and P0173 means that the system tried to go outside of the fuel trim limits.

Now this can be usually caused by a bad mass airflow sensor, but there's number of other reasons why the engine cant stay with predefined fuel trim limits. There might be an unmetered air in the system, an injector could be faulty, lambda probes might have shifted charactereistics...indeed, in most cases it's the MAF itself, but careful - i've got some returning customers after "quick and dirty" diagnosis of faulty airflow sensor.

As for the sensor itself, of course it's nice to put an OE part but installing a quality replacement (like, from BOSCH) will not cause any problems.

The fuel trim will eventually level off in the correct area after fixing the problem but this might take some time. It's advisable to reset the fuel trim adaptation after replacement of the airflow sensor. NOTE that this should not be used as a cure for bad idle/engine running problems, since if the problem is not solved and you reset the adaptation, it will actually make the engine run WORSE than before.

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RE:

error code P0170, P0173?

My 01, E320's CEL come on few days ago, the error code is P0170 and P0173--fuel trim malfunction on

bank 1 and 2, the shop already told me about the cost to fix it, but I would like to have a second opinion

Anyone?

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Those codes indicate that the fuel mixture mapping is out of limits. There are many possible causes. By themselves they are of little value and if there are no other stored codes they may be transitory. A tank of bad gas can trigger them and they will clear in a couple of tanks of good fuel. You need to take it to a Benz dealer and have them put it on their diagnostic computer. A cheap hand-held code scanner can't pull all of the stored codes or many of the Benz-specific sub-codes that may shed light on what is going on.

Fuel Trim Malfunction

you have a bad maf (mass air flow sensor). you can change it yourself, it takes about 1 min and it is as easy as pouring gas in your car. cheapest whole maf unit i have seen for your 01 e320 is $175 at http://www.autohausaz.com/search/product.aspx?sid=... %26 Air System&gid=5068@Air Mass Sensor and they have free shipping for orders over $50. also don't forget to change air filter (if is dirty) while you are there.

you can also change just the sensor, the sensor is cheaper (~$140) at www.germanstar.net , call him. best would be if you changed whole unit from autohausaz which i mentioned above.

the check engine light will go out by itself after a couple days, or you can just go to autozone and they let you use their code reader for free, and you can erase the codes with that. good luck.

Go to constellation in pasay they give reasonable quotation and they are good. Had the same prioblem before