kfer

Hello everyone,

I just bought a 2007 C230 with 64k miles. Very clean inside and out; it drives and stops perfectly…no noises, pulls or rattles. The engine runs silk-smooth….but…I drove it home from the used car dealer (45 miles, it was very low on fuel)…pulled up on my drive way (kind of steep) and when I put it in park….bammm…the dreaded check engine light (CEL) came on!! The car still drives and runs the same…there’s no difference between before and after the CEL. The air filters appear to be clean; I’ve checked for disconnected hoses, unplugged connectors, debris on the MAF sensor…everything seems to be in working order.

I retrieved the codes (Autozone) and they are:

P0170 Fuel Trim Malfunction (Bank 1)
P0173 Fuel Trim Malfunction (Bank 2)
P0178 Fuel Composition Sensor Circuit Low Input

Would low fuel level trigger a CEL?
It’s possible that someone put 87 fuel on it. Could this trigger a CEL?

I filled the car with premium fuel and have driven approximately 100 miles on it with 3 "cold, overnight engine restarts" in between. The CEL is still on.

Do I need to log more miles, engine restarts, with the right fuel for the CEL to clear?

I’d greatly value any comments/advise on this issue. Thank you.

LILBENZ230

I would continue to drive for now and see if it clears. The fuel composition code is what doesn't make sense. Since the 07 C230 is flex-fuel that sensor should determine the amount of ethanol in the gas and adjust things accordingly. Have you re-scanned the code? Re-scan it and see if the fuel trim codes are still showing. There may be a problem with the composition sensor, I'd contact the dealer who sold the car in that case because they likely reset the light without fixing the problem.

Peydidy

Oh wow what a bad way to start off a new car. Well hope it gets figured out and welcome to the forum!

kfer

Today I'm going to buy an OBD scanner with "clearing" capabilities. I'll check to see if I have the same, fewer or new codes and will clear them. I'll post the results.

Any recommendations on a OBD scanner would be appreciated.

Thank you.

LILBENZ230

Anything CANBUS capable should work fine, even the cheap ones.

phister

Yup harbor freight sells cheap good ones

kfer

Well, I went to NAPA and picked an Innova 3020 OBD CAN scanner. I plugged it in and retrieved these 5 codes:


P0170 Fuel Trim Malfunction (Bank 1)
P0173 Fuel Trim Malfunction (Bank 2)
P2006 MAF sensor disconnected with engine running
P0170 Fuel Trim Malfunction (Bank 1)
P0173 Fuel Trim Malfunction (Bank 2)

The scanner gave me an amber light as well (the scanner has 3 lights: red - failed emissions test; amber - pending codes; and green - pass emissions test).

I cleared the codes and the Check Engine Light (CEL) went away. I re-read the codes and they were gone.

These are my questions:

Has the car stored the codes waiting for the malfunction to occur again after a pre-determined number of "starts"?

If the malfunction doesn't occur after the pre-determined number of "starts or cycles" do the codes go away and the car will pass the emissions test?

Thank you again for your advise.

phister

once you clear the CEL, it'll take a couple of cycles of the car being turned on to come back on or after a certain amount of driving. If they are real CEL they will come back on. but you should check your MAF to make sure its properly connected. That might be causing the issues. anything like a loose intake can cause CEL and make the MAF read off.

jrod73

What is the definition of WAF?

TruTaing

Mass Air Flow Sesnor. Seems like yours is dying or getting lazy. This was a common issue w/ the m112 motors, but this is the first instance I have seen w/ the m272 - Try out the w204 forums also, they have a bit more experience/exposure to the m272. Good luck - do report back for the m272 w203 guys

LILBENZ230

Yep the MAF could cause these issues so make sure it is properly connected.

jrod73

Where is the MAF located? Is it the sensor inside the vent where the air filter manifold connects to the engine?

phister

Remove your intake and it's on the back of the engine by the firewall. It'll have the wire mesh covering it.

kfer

Today I've driven the car 50 miles with several engine starts, both in traffic and on the highway. The heat in Houston has been brutal.

So far so good...CEL still off. I used the OBD scanner and checked again...no malfuntion codes but still get the amber light: pending codes.

Last night I had 4 flashing "abbreviated codes" on the upper left corner of the scanner; today I only have 2 such flashing codes after driving the aforementioned 50 miles: "EV" and "2A".

I'll report any developments.

On a separate note, I went to the dealer to buy rubber floor mats ($110) and the spare tire lug bolts lit ($32) that were missing. I know I could've gotten a better deal online but felt really uneasy driving around without the bolts to change a flat tire and messing with the original carpets which are in "as new" condition. I had to buy those items now.

A cute girl in the service department ran the VIN to check the car's history: 2 previous owners who both took the car to the dealers in the are. All services A and B were done on a timely manner; however....I need to do change the spark plugs ($275), transmission service ($375) and differential service ($139). Nothing outrageous except for the spark plugs...how difficult could these be to charge $275?

Anyhow, I'll keep you posted with news of my Benz "Christening"....

phister

you can do all that stuff yourself for wayyyy less. all of those are in the DIY section at the top of the forum. Very easy things to do.

jogger

i think spark plugs need change at 100k, check the manual

phister

plugs are at 100k, and get the OEM bosch plugs

Norwichdelta06

i dont know about TEXAS laws but in NY you have a 3 month 3000 mile warranty on any used car you buy from a registered Dealer in NY.

kfer

So far so good (wishful thinking), no CEL but...yesterday morning I checked the codes again and found two codes labeled "pending": P0170 and P0173, and the flashing "EV". The OBD scanner still deems the car amber - pending.

I drove another 50 miles of mixed traffic and highway, no CEL and arrived home last night and checked the codes again: no codes, only the flashing "EV".

The engine is very smooth and powerful in all RPM ranges, fuel consumption seems to be normal, no smoke or smells of any kind.

Any thoughts?

Thanks.

kfer

Last night I checked the codes after I got home: the "EV" stopped flashing but I the OBD pulled codes P0170 and P0173 again...but no CEL on.

This morning, just before I made it to the office, the CEL came back on. Read the codes and found these four:

P0170
P0173
P0170
P0173

I bought a can of CRC MAF cleaner and will clean the MAF thoroughly as a last resort. If this doesn't solve the problem I will buy a new MAF sensor.

I will post a follow up....

rtai

I totally understand the problem happened to you because these two codes are bothering me after I changed both my air filters on my 2007 c230 last week. I borrowed an Innova 3100 scanner and erased, but came on again 2 days later.
Therefore, I am going to trying to clean MAF which most people here recommended.
Before this, I got to know how to disconnect the MAF. It seems a challenge to me because I can't find any info related to c class. Hopefully I won't break the MAF house or the plug.

Take care.

phister

make sure the intake is properly seated on the MAF and that there are no leaks or gaps in the intake. if you have a slight gap and letting in unfiltered it'll make the MAF read all crazy. had a cel once saying i was running rich because I didnt fully push the intake snug on the MAF.

But sounds like the MAF is goin to crap

JJSBENZ

Were you able to solve your problem? I just replace the air filters on my car and now getting the same faults P0170/P0173.