TruTaing

My check engine light just suddenly came on when I came to a stop.

No funky noises. Engine is running fine. Braking was normal. Heating was normal. No malfunctions showing on my dash. Oil was changed pretty recently - maybe 2 months ago. New air filter was put in recently.

I drove for another maybe 30 miles to get home. Nothing else went nutso. I tried turning off the car then startin it back up, CEL still on

Im worried the thing is gonna like suddenly blow up.

Anyone know how much itll cost for me to take it in?

Or does anyone have suggestions as to what to look for???

halps!

m-benzw203

take it in and tell Benz to give u a ready on the light very easy and quick good luck b/c the problem can be anything

Moviela

If you have an AAMCO transmission shop near you, drop in and ask them to plug in the scanner. They should do it for free if you tell them you heard it on the radio. They will at least tell you if the washer fluid is low, or something more serious.

jtC320

wow..i didn't know that they do a free scan...last time i went, they charged me $25 to scan and when the analysis came out to be a loose bolt on the exhaust...

dalazernet

I had the CEL come on a week or two ago... I panic'ed since my old Grand AM's check engine light meant "pull over immediately and tow me in!"... but Mercedes ran their checks and it was a minor emmisions leak - they said most likely due to the gas cap not being on fully. Did you just get gas recently? I didn't, but I suppose it might not have been on perfectly.

Their advice to me, which I extend to you -- if the car is driving normal, take the gas cap off, put it back on and drive it for 2 (two) more days or so - the light should go off by itself. *sigh*...

Thats direct from the dealership

- Eric

Trekman

go to autozone and you can rent the scanner for free. it will tell you the code and the problem, reset it and see if it come back.

TruTaing

I can rent the scanner? That sounds very interesting. Do you think they would be willing to just check the thing out for me? Ill check that out today.

I bought the mercedes WIS service/repair manual on dvd. I have access to all of the codes and what nots. Having access to the scanner is what I need!

Ill try the gas cap thing today also because i DID recently put gas in.

thanks! updates to come.

TruTaing

Ah, so ive tried the gas checking the gas cap and nothing has changed thus far. After you waited two days did it go away?

Just kind of a general question about CEL's. My father insists that there are two kinds of CEL's. A yellow one and a red one. He says he was told this by a tech. the red one is bad. something about your engine. but a yellow one is a sensor malfunction. Do you guys know if this is true or not?

thanks!

mleskovar

Never heard of two different colored CELs on the same car...buy yourself a scanner, just make sure it's one that can clear the codes...about $35. A good investment since every car since 1996 is required to have an OBDII port. Sometimes you clear a code and it doesn't return. Some codes will put your car in "limp home" mode where it won't shift past second gear. Simple to use...just plug it into the OBDII port under the dash next to the steering column to get and clear codes.

Buellwinkle

If you get the codes with now text, I have the MB codes on my website.

TruTaing

I dont mean like two difference CEL lights. One CEL thing on the dash, but it lights up in two different colors. I dont know if there is truth to what my father has been insisting, but anyone who has looked behind the instrument cluster would know the answer to this

What do you mean clear the codes? I have never used/seen one of these scanners before. But, i know that there are 'codes' that determine the malfunction for your vehicle and im guessing the scanner is capable of clearing these? Where could i buy one of these scanners and be sure that it would work with my car 01 c320? Do i have to buy software for it also?

thanks!

Moviela

If the drivetrain management computer reads a problem, it records in local memory a number that represents the malfuntion it encountered. An OBDII (On Board Diagnostics II [2]) scanner can read the memory and display the codes. With that information you can do pinpoint tests for the fault displayed to identify the bad part. Sometimes you will encounter an intermittant fault, so clearing the memory will extinguish the check engine light until the fault occurs again.

You can buy a scanner in autoparts store, Sears, Online, or make one yourself. Prices range from very simple ones for 40. to 200. or Top of the line from Mercedes for about $ 15,000 with software license.

Most of them indicate which vehicles they can scan. Some only do "basic" scanning, being that required to meet government standards. Other scanner can check extended functions added by manufacturers to assist workshops with servicing the car.

bViC

this might be a stupid question, but did you make sure your gas cap is tight? cause if its not, it will set the light off. it takes a few days for it to go off once everything is sealed.

TruTaing

Yea, i did tighten it... but the light hasnt gone away. Is that a few days of driving? or a few days later, period? cuz i dont know if i want to continue to drive the car around if its got issues.

mleskovar

[QUOTE=TruTaing]What do you mean clear the codes? I have never used/seen one of these scanners before. But, i know that there are 'codes' that determine the malfunction for your vehicle and im guessing the scanner is capable of clearing these? Where could i buy one of these scanners and be sure that it would work with my car 01 c320? Do i have to buy software for it also? [QUOTE]

You can buy them at any auto parts store. Get an inexpensive one...I bought an Actron CP9125 on sale for $39 at Krayco. All cars since 1996 have the port (under the dash next to the steering wheel usually). It is a self contained unit with a cable and compatible plug. It came with a CD containing the code descriptions. Make sure it can erase codes so the CEL and "malfunction" display will go out. You plug it in to your car and read the code directly from it then match the code to a malfunction. Any OBDII scanner will work on your car....they're generic. Some codes are MB specific and you'll need a reference...like Buellwinkle generously offered.

StapleGun

Make the investment in an On-Board Diagnostic (OBD) II scanner -they're dirt cheap now and will pay for itself in a couple uses - check the "bay". El Paso tool has 'em for $39.99 give or take. Also for everyone's 411, the CEL is not a critical indicator, it's set up for warnings of emission-type components, i.e. catalytic converter, O2 Sensors, gasoline cap, EGR, PVC valve etc...they indicate that they are in need attention but will NOT immediately cause damage to your engine in the short run.

TruTaing

So, I had my car taken into the place where i bought it, and the tech used a tool to get the codes out and what nots. He said eventually that it was some problem w/ the gas trim. I dont know exactly what that is, but he said it seems to just be a simple malfunction.. he went on to just reset the CEL. Im not quiet sure what this gas trim is and what it does, but Ive done some basic googling and still havent found anything useful.. although i have found many mentions of the gas trim and a stepper motor together.... My car makes that funky noise from behind the stereo... everyone says that is a pain in the *** to fix and caused by something broken w/ the stepper motor... Sadly i was not present while my car was taken in due to conflicting schedules with work and the place i bought my car and i wasnt able to ask the tech exactly what was going on.

Does anyone here know exactly what a gas trim is and how it works? or if it is effected by new k&n air filters ive put in or if my stepper motor has anything to do with it?

Its one thing to have the CEL light turned off... its another thing to understand what exactly is goin on :\

anything would be helpful!

thanks,

mleskovar

Could be directly related. Too much oil on the filters can find its way to contaminate the MAS which is one of the things that control the fuel trim. See, if you had a OBDII tool you could have just as easily reset the CEL and it would have already paid for itself in time and money......

TruTaing

Ah, i fully intend to buy myself an OBDII scanner. I just called the place that i bought my car from cuz they are cool w/ helpin their buyers out. Didnt cost anything and I figure i could shop online a lil more and buy a 'better' scanner..

The thing w/ those filters is that i put them into my car right out of the packaging. I would imagine that they wouldnt have excessive ammount of that oil on it. :\ I would imagine at least. I could imagine putting on too much oil after i clean the filter... but not when i put them in brand new out of the box. i ono do you guys have a specific brand of OBDII scanners you guys would recoomend?

Buellwinkle

A fuel trim code can be more serious than he lets on. What it means is that the engine was running so lean (the more likely) or so rich and it wasn't able to make the necessary adjustments to compensate. This could be a sensor that's on the edge of going bad like an O2 sensor giving wrong results but good enough not to throw an O2 sensor code, a vacuum leak, weak fuel pressure, dirty injectors, etc. Keep an eye on it, make sure you're not getting poor fuel mileage or poor performance.

mleskovar

I recommend the cheapest one that has an erase function. You can get fancy all the way up to the MB SDS system but the basic functions of displaying the codes and clearing the memory is all you really need IMHO. I agree a K&N right out of the box <shouldn't> have excessive oil in it.....are you sure you put the air box back on correctly? I'm not a K&N fan because of the oil and I doubt any improvement to airflow is even needed. The MAS is positioned just after the air filter box and susceptible to oil contamination. But once again, it's only one of the things that control fuel trim.

TruTaing

ive actually had great gas mileage after puttin in the new filters.

I think my car on fueleconomy.gov gets 19city and 25 highway, but after ive put the filters in i was gettin more like 20 and 25.5. its definately not an exact figure, but prior to puttin the filters in i was averaging around 23.3 mpg (i noted this) and since i put in the new filters i was gettin on avg 24.5....

so i guess this helps me narrow it down to a sensor problem. O2 or MAF? right?

thanks!

TruTaing

Yea, ive done a bit of shopping and they all seem to do the same thing... some just have cooler accessories and what nots, but not really required things. Im pretty sure i put the air box back on right, and i have seen the MAF myself. Ill check it just incase, but i put those AIR filters on almost 3 weeks ago. I figure that if i put the box on incorrectly the car would have been complaing immediately.

What else controls fuel trim? After more research i know the MAF and O2 sensors can affect fuel trim?

Buellwinkle

Sure, you can throw all sorts of money on sensors and maybe you'll get lucky. You just have to ask yourself, are you feeling lucky? Keep in mind you have a federally mandated emissions warranty for 80K miles. Think about what the O2 sensor is doing, it's telling the ECU your engine is running lean, the ECU sends a wider pulse width to the fuel injectors, the O2 sensor tells the ECU that it's still lean, the ECU reaches a preset maximum and and says I reached the maximum pulse width and can't send more fuel and throws a fuel trim code. So this is were we seperate the mechanics from the wannabees, is it the O2 sensor providing the wrong info (the obvious choice, shoot the messenger)? Are the injectors clogged to the point they can't deliver enough fuel? Is the fuel filter dirty, fuel pump weak or fpr faulty and not providing enough fuel pressure to the fuel injector? My suggestion is easy, put a diagonostic scope on the injectors to measure pusle width, see if it's even between all injectors, see if it's goes up if you disconnect a vacuum line, see if it goes down if you squirt propane in the intake. Put a pressure gauge on the fuel rail, are you getting about 50 PSI, less, more? Get a log of sensor activity as you drive, is the O2 sensor giving reasonable readings?

mleskovar

Disclaimer...I'm not a career mechanic like some people on this forum but I've studied engineering and done all my own car and motorcycle maintenance for 45 years including engine and trans rebuilds. I'm not doubting your gas mileage increase but find it hard to attribute it to the air cleaner unless the one you removed was partially blocked. If a manufacturer could get better gas mileage with such a simple fix don't you think they would do it? Standard air filters pass more air than engines can use and in this case, offer better/finer filtration. Anything that affects the air/fuel ratio affects trim is the simple answer....there are many things, that's why there's an on board computer(s) to control all the inputs and make the decisions to keep the engine at peak efficiency and within pollution guidelines. I'm averaging 26.5 mpg overall at 100K miles and it keeps getting better as the car ages!