Check Engine Light on C230
 

My check engine light came on at 75,000 miles. I checked the problem with a code scanner. The result was an error code of P170. There are mulitple fuel errors for this problem code. Any ideas where I can start with this one? The car runs fine until higher RPMs, then she misses a little.

You won't get a definitive diagnosis without using SDS to read the adaptation, but it does sound like your Air Mass Meter is going south. Common problem on OBD-II cars, and especially on 1996- Mercedes models.

It's most likely the AMM or the fuel pressure regulator. I'd put my money on the AMM.

Here's how you tell...

1. Read the adaptations for fuel trim. If 1.15 or over, it's most likely that you need the AMM. If under .85, most likely the fuel pressure regulator.

2. If adaptation values are high, replace the AMM with a new unit and test drive the car. Recheck codes and adaptation values. If the problem is solved, voila!

3. If problem persists, then you've got to look elsewhere.

BTW, the AMM is about $300USD and take about 5 minutes to install. You'll probably have to spend some dough on diagnostic work, but it's better than throwing parts at a problem.

Keep us posted and good luck...

Is it fair to say that most of the "wear" of the AMM occurrs at turn off when it "heat-cleans" itself. If this is the case then their life would probably be more closely related to days or years than miles. If so, about how many years do they last? I think mine went after about 3 years.

Mike

My AMM was replaced at 163,000kms (about 101K-miles) and 6.5 years.

P0170 is an air leak on the intake/air system/fuel pressure or pump/injector(s)/o2 sensor

this is a standard code when the engine doesnt start like over fueling there is probably no problem at all but you need to reset the codes to find out