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2007 C230 Sport
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Discussion Starter #1
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.
 

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i would clear the codes (which will turn the light off) and see if it comes back on. you can clear the codes with any scan tool (autozone will do it too). low fuel level won't make it come on. low octane fuel possibly but not necessarily those codes (it could cause detonation though if hot and high engine stress).
 

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2014 Mercedes-Benz C300, 2006 Lexus IS250 AWD, 2006 Land Rover LR3 SE, 2000 Ranger R83
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Amazingly enough I have an 07 C230 with 70K and the CEL came on yesterday also. Hooked up my Actron code reader and it read the P0170 code. Talked with 3 mecanics and they all recommended putting fuel injector cleaner in a tank of gas (which I did) and clearing the codes (which I tried, but my scanner won't remove the code). I was told that the fuel trim was the computer telling the injectors how much gas to inject into each cylinder. There is a short term & long term trim. Short term is right then & there and long term is basically how you normally drive the car. Was also told that as long as the light wasn't blinking I was OK and I wouldn't blow up the car or anything. Wouldn't be that big a "pain in the butt" except that I'm driving from Kentucky to Virginia Beach to Gaithersburg MD and back to KY next week.
 

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2007 C230 Sport
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Discussion Starter #4
OBD Scanner

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.
 

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2007 C230 Sport
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Discussion Starter #5
Bought the OBD scanner

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.
 

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OBDII error codes occur whenever some sensor's feedback is beyond the expected range of the ECU. Sometimes these errors are transient (momentary burps) possibly due to bad fuel, a loose wire, loose gas cap, a bug sucked into the intake, or some other oddity. the ECU is programmed for some amount of tolerance to eliminate most transient errors, but if it lasts long enough or happens enough times, it will illuminate the MIL. If the error is transient and never occurs again, the MIL will be extinguished after some number of engine cycles (3 to 5). However, the occurrence of the error is still stored in memory. If you clear errors with a scanner, they are totally cleared - there is no trace of them ever having occurred. The memory is erase.

As long as the errors were transient, then all is fine except for one problem. There are "readiness indicators" that OBDII provides to let emissions check centers know that the vehicle's system have operated for enough miles/hours and have reach a full operating range of operating values. If you clear the errors, you also clear the readiness indicators and you won't pass an emissions test until the engine goes through enough operating conditions to "check off" all of the readiness indicators. Of course if those errors truly were transient, then you will be able to drive the vehicle enough to set the readiness values and not trigger an MIL. However, if there is a problem, then the MIL will be illuminated when the error condition returns.

Given your information, I'd say you have a failing MAF sensor. My first step would be to try MAF sensor cleaner, but the reality is, that often does not work on MBZ's as their MAF's are very sensitive. Also, your error indicates more than a dirty MAF, but possibly a broken sensor.
 

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2007 C230 Sport
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Discussion Starter #7
Thanks!

Rodney,

Thanks for your thorough explanation. Along with the OBD scanner I also bought a can of CRC MAF cleaner. If the CEL comes back on I will clean the MAF, clear the codes and see what happens.

If I end up needing a MAF sensor, what vendor would you recommend as far as quality vs. price?

Let's say I replace the MAF sensor, clear the codes....what else do I need to do? Some threads talk about "resetting the ECU"...is this a separate procedure in a 07 C230?

Thanks again.
 

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I have heard of the need for some sort of ECU reset when replacing the MAF sensor, but I can't find anything in WIS related to that. As for brands, you need OEM or Bosch. It will run about $300. Don't bother with the $80 eBay specials - they don't work.
 

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Discussion Starter #9
No CEL today

:)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".... 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"....
 

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I am thinking those 4 "pending codes" are the readiness indicators. I guess your driving has met the conditions to clear two of them, but not the other two. Maybe the manual for your code reader explains them?

As for plug and other services needed, you can download the maintenance schedule here:

MBUSA 2007 C-Class Maintenance Manual

You will see that the transmission fluid/filter change is due at 39K miles. MBZ only calls for it to be done once at 39K, but after seeing how dirty mine was, I'd strongly recommend doing it every 39K. Spark plugs on the M272 engine are due at 91K or every 5K miles. And that is not a $275 job. It's a not too difficult to DIY. Transmission service can be a DIY if you really want to, but $375 is not bad (it will cost you over $300 for the parts and tools the first time, then just over $100 each time after that). Oh, adn I see not mention of differential serive. That's uusally good for life, unless there's a problem.
 

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pending codes mean an intermittent fault was detected which was not significant enough to turn the MIL on. if it recurs the MIL will come on; if it doesn't recur after some time the pending code will go away.
 

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SO why doesn't it give a standard OBDII P-code instead of these four lights? I am not familiar with these generic scanners - I've always used the vehicle manufacturer's systems (like SDS). It doesn't have any such indicators. There is either an "active" error code that has illuminated the MIL, stored error codes, or none.
 

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Discussion Starter #13
Day 2, no CEL yet

Today I filled up again with premium fuel (needless to say) and drove 25 mixed miles. Returned home and checked for codes again. No malfunction codes and the two flashing "pending codes", "2A" and "EV", are down to one flashing: "EV".

I hope some more driving under the right conditions will clear the flashing "EV" code and move the car from amber to green - pass emissions.

I'll report any findings.
 

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Discussion Starter #14
Bad news

Last night I checked the codes after I got home: the "EV" stopped flashing but 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....
 

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Discussion Starter #15
CEL on again

I cleaned the MAF sensor woth CRC MAF Cleaner, reinstalled and cleared the codes.

Well, afte a couple of days the CEL came back on. Rechecked the codes and sure enough:

P0170
P0173
P0170
P0173

Based on several responses to my initial inquiry I went ahead and ordered a new Bosch MAF from RMEuropean.com ($175, free shipping).

What do you guys recommend to be the proper procedure to install a new MAF so the main computer recognizes it? I was thinking to install it and clear the codes. Is this enough?

I really don't want to ruin a new MAF!

Thanks....
 

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That should be all that is needed, i.e. clear codes and go. Just be careful with the new MAF. If you ordered the MAF installed in the intake tube assembly, then there's really no worries on damaging it as it's well protected. If you have to install the insert into your intake tube, then just be careful not to touch it or get any dirt in it.
 

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Discussion Starter #17
Success

I installed the new MAF sensor last Thursday. I took the precaution of disconnecting the battery (just in case) prior to installation.

With the new MAF in place, I turned on the engine and cleared the codes with the OBD tool. With the damaged MAF the engine was smooth and powerful....but with the new MAF...wow...you can hardly tell the engine is on...and the car now has a better pick up at lower revs.

It took about 100 miles of mixed driving to clear all the readiness codes that were flashing in the OBD tool. "EV" was the last to clear last nigh and the OBD tool gave the much coveted green light: "pass emissions"!!!

I'm looking forward to having a couple of months of care free driving in this sweet car.

I'd like to thank all the members who provided answers to my initial inquiry.
 

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Part number is A2730940948. It's fairly easy - just a few vacuum hoses to remove and the plastic clip. Those hoses and the plastic clip can be very brittle, though, and may break when you try to remove them. Luckily, they are fairly inexpensive to replace.
 
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