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Check Engine Light

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monarchd's picture
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I have a 1998 C 230. Recently the check engine light came on. I plugged in my code scanner and retrieved a code P170. Which is defined as "Fuel Trim Malfunction, Left Bank." Does anyone know what my next step would be? I have checked the engine vacuum and it reads 15 - 17HG.

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Anonymous
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I had the same thing on my 1997 C230 at 75,000 miles, and it ended up being the air mass meter. My understanding is it's very common. My indie replaced it and turned off the check engine light... no problem for a year and a half.

I'm not sure on the steps, but I bet you could order the part and do it yourself.

There are other sources of information on the Internet that may be very helpful to you. I would search under "mercedes shop."

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Jim Seeger's picture
Edmond, OK
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Joined: April 18th, 2003

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339

Vehicles
2003 ML350
1994 E320 Wagon
1993 600SEL

Is it fair to say that you can, reasonable competence assumed, replace the air mass meter(s) yourself? Does this not require electronic verification of installation/reset functions?

1993 600 SEL, 113K
1997 Chevrolet Tahoe, 118K
1967 Chevrolet Camaro Convertible SS/RS, 67K
1964 Ford Thunderbird, 109K
1965 Dodge Power Wagon, 96K
1960 Chevrolet Apache, 106K
1956 John Deere Model 70
1949 International WD-9
2002 Honda VTX, 8K

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Jim Seeger

Anonymous
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David, the same thing occurred on my '98 E320 about 3-4 months ago at about 65K miles. Evenually I had the codes read and they were the same as yours. My independent mechanic said that everytime he's seen those error codes it has always been the mass flow sensor.

I purchased one from my dealer for less than $200 and installed it myself. There's absolutely nothing to installing it. It took me all of 2-3 minutes. After I installed it I returned to Autozone and had the codes reset. My check engine light and message has been off ever since (about 1 month).

I've attached a picture of my mass flow sensor, in case you're not familiar with it.

For lots of information on this topic, go to mercedesshop.com, technical forum, and search on mass flow.

Dave

Anonymous
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Oops, the attachment wasn't included. Here's a picture of the mass flow sensor.

mass air sensor.jpg
Anonymous
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Anonymous's picture

Hi your code p0170 means long term adaptation to limit value(self-adaptation of mixture formation) i would not condem the mass air flow sensor with out testing it or at best have code cleared ,reset adaptations. Bad gas low octane vac leak can all cause this condition if you had a code p0101 that would be the hot film sensor in the mass air flowcause for replacement.joeym I would check with Tom but i think the mass air on your veh is much more then $200.

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