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600 SEL Check Engine Light

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For you W140 600 SEL owners, I have decided to remove the bulb that lights up the "check engine" light. My MB technician has spent two years trying to figure this one out. Both air mass meters have been replaced, etc. Everything else checks out. The car runs perfectly. Any other suggetions before we pull the bulb?

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A working check engine light may save your engine in the future. Does your mechanic have the equipment to read all the stored DTC's? And even more important, does he know what they mean and have lots of hands on experience with your particular model?

After two years of troublefree ownership the check engine light came on on my '99 S600. The problem was a vacuum leak in the evaporative system. There was no pressure in the fuel tank so the DTC was erased and a new fill cap was installed. The light came on a few days later . Next a vacuum line was replaced under the intake manifold. A Switchover valve leaking dampening fluid was discovered. Code cleared and new switchover valve replaced. Several days later the light came on again. This time car couldn't hold vacuum from engine to valve near charcoal cannister behind left rear wheelwell. New valve installed and code cleared. Several days later light came on again. I replaced 8mm nylon evaporative lines on each fender well as well as both purge valves. The light went out on its own after several days driving. I think that the 8mm lines had shrunk in length as they were pulling out of the purge valves.

It has been about 6 months since and the light is still out. If the cause of the problems is remedied the light will go out after 4 "drive cycles". A drive cycle is starting out cold, driving till warmed up through all the gears and then cooled down.

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New York club member since 1976.

Continuous Mercedes ownership since 1964.

1993 300SD with '99 606 engine. 111,040 miles.
1994 S350   75,238 miles
1995 S350 148,124 miles.
1996 S420 with '99 606 engine  Sold
1999 S600  one of 14 imported  Sold 
1989 Bentley 8  Sold at 40,000 miles.

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1994 E320 Wagon
1993 600SEL

Thank you for your response and the information. I will share this w/my MB technician. I prefer not to remove the bulb and will try anything reasonable.

If we locate the culprit, or not, I will advise. Thanks again.

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One area that was checked during my check engine light problem was for a leaking intake manifold gasket. Joeym7 says that they could sometimes be causing the vacuum leak. Luckily it wasn't the problem. He claims that removing the intake manifold to replace the gasketing is labor intensive. Most mechanics have a trick for detecting leaking intake manifold gaskets.

__________________

New York club member since 1976.

Continuous Mercedes ownership since 1964.

1993 300SD with '99 606 engine. 111,040 miles.
1994 S350   75,238 miles
1995 S350 148,124 miles.
1996 S420 with '99 606 engine  Sold
1999 S600  one of 14 imported  Sold 
1989 Bentley 8  Sold at 40,000 miles.

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600SEL check engine light

Unsure the similarity between a 1992/3 600SEL v12 and a 1999 S600 v12, if the vacuum hose routing to the evap. system are the same. Many differing conditions can cause a check engine light to cycle on/off. Checking the DTCs is a good idea. Other engine monitoring sensors remaining intact even if the check engine light bulb is removed, as I did on my 1993 600sel w/new engine, to warn the driver of serious engine defect conditions.

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1994 E320 Wagon
1993 600SEL

Today I again spoke w/my MB technician about this. He recommends that I leave the 600 with him for a day or two so he can track down the "red check engine light" culprit. I think I will try this before removing the bulb.

As a side note: a few weeks prior to the "red check engine light" first coming on, I changed the air filters to K&Ns. After the light first appeared, I was advised by other MB owners NOT to use K&Ns--the reason given was that these filters would ruin the air mass meters. My MB technician, however, does not think that the K&Ns had anything to do with the air mass meter problem.

During the time that the K&N filters were being used, the codes originally read that one of the air mass meters needed to be replaced; that "fixed" the red light for about two months, then, the "red check engine light" again came on. The codes then read that the other air mass meter needed to be replaced---which it was. At that time, I pulled the K&Ns and reverted to the OEM air filters. All during this period, and now, the car runs good.

Perhaps the "red check engine light" has found another culprit besides, or in addition to, the air mass meters.

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Maybe the K&N filter ruined the first air mass sensor you replaced. You stated that you kept running the car with the K&N till the second air mass sensor was replaced. It would be a shame if you had to buy a total of three.

As a point of info the air mass sensor on the drivers side is for the curb side cylinders and the curb side one is for the drivers side cylinders.

__________________

New York club member since 1976.

Continuous Mercedes ownership since 1964.

1993 300SD with '99 606 engine. 111,040 miles.
1994 S350   75,238 miles
1995 S350 148,124 miles.
1996 S420 with '99 606 engine  Sold
1999 S600  one of 14 imported  Sold 
1989 Bentley 8  Sold at 40,000 miles.

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

Posts:
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2003 ML350
1994 E320 Wagon
1993 600SEL

Yesterday I picked up the 600 SEL from my MB technician. The check engine light, I hope, is now solved.

After running diagnostics he noted that the left bank air mass meter was not gaining temperature as it should. This is the first time I ever heard of this, but he switched the left side air mass meter to the right side and visa versa--he said that he also removed the computer connections, cleaned and reconnected them. The codes are clear, the car runs perfectly.

Is this a false-positive? Has anyone heard of this "fix"?:D

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I would have figured both air mass meters were the same part number so a switch is a reasonable trial in diagnostics. I have seen this issue also resolved by just carefully cleaning the mass air flow meters and then cleaning and checking the connections not only to the mass air flow meters but as many of the sensors as possible.

One normal problem with sophisticated engine computer controls is you repair one issue and another surfaces due to odd reasons. Clearing the codes and computer completely by battery terminal removal usually helps and an engine check light reoccurrence again with same error code usually means the basic problem was not fixed. Also a common situation.

Drive the car for awhile, monitor, maybe you got lucky.
Bill Mercer

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Conrad,

Under no circumstance would I remove an engine warning lamp (or any critical system like ABS etc.). An ext lamp warning is a different story. It may be annoying (just be thankful there isn't a buzzer to go with it like the seat belt warning), but it's there for a reason.

If necessary, spring for a trip to the dealer. They have to solve it.

There may well be a time when something else goes wrong in addition to what the computer thinks is wrong now. Or this is a very early warning of something serious that your tech just doesn't know about. Even my 560 stumps the dealer techs once in a while, but they have the rescources to eventually deal with it. (It had them scratching their heads for a couple of days once.) I'd hate to have to replace my engine let alone a 600! But you need that light and you need it to work the right way.

Just my 2 pence.

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signed-Bill Mercer.

I would have figured both air mass meters were the same part number so a switch is a reasonable trial in diagnostics. I have seen this issue also resolved by just carefully cleaning the mass air flow meters and then cleaning and checking the connections not only to the mass air flow meters but as many of the sensors as possible.

One normal problem with sophisticated engine computer controls is you repair one issue and another surfaces due to odd reasons. Clearing the codes and computer completely by battery terminal removal usually helps and an engine check light reoccurrence again with same error code usually means the basic problem was not fixed. Also a common situation.

Drive the car for awhile, monitor, maybe you got lucky.
Bill Mercer

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Quote:
Originally posted by Dave Moyssiadis
Conrad,

Under no circumstance would I remove an engine warning lamp (or any critical system like ABS etc.). An ext lamp warning is a different story. It may be annoying (just be thankful there isn't a buzzer to go with it like the seat belt warning), but it's there for a reason.

If necessary, spring for a trip to the dealer. They have to solve it.

There may well be a time when something else goes wrong in addition to what the computer thinks is wrong now. Or this is a very early warning of something serious that your tech just doesn't know about. Even my 560 stumps the dealer techs once in a while, but they have the rescources to eventually deal with it. (It had them scratching their heads for a couple of days once.) I'd hate to have to replace my engine let alone a 600! But you need that light and you need it to work the right way.

Just my 2 pence.

Dave

We did not remove the Check Engine light bulb! The good news is, is that the light has not reappeared!

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600

If the problem does happen again,have your tech inspect the rubber boots that attach the airmass to the throttle actuator.The boots can dry rott over the years and form small cracks not noticable until removal.These small cracks allow unmetered air into the engine.When the fuel computer notices this, via the 02 sensors,It throws a check engine light-the code stored would be for air mass sensors.

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I faxed a copy of your email to my MB technician for future reference. My check engine light is still "off". Thank you for the hint. :)

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The light is back on . This morning I started the car ('93 600 SEL) in preparation for a short trip. There it was again--The Check Engine Light. I have already returned it to the MB technician for another look.

Attention: AS199! The rubber boots are fine. Thanks again for the suggestion, though.

Any other ideas are welcomed!:confused:

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If it is the same code for airmass sensors,it is most likely not hte airmass sensors.You have a vacumn leak somewhere.With the car running spray carb cleaner around the intake and see if the idle raises.If it does you have verified your leak.I belive that the 120[V-12]engine has rubber vac lines that run inder the intake that are prone to leak with age.The system works when the airmass sensors measures incoming air.With this measurement the fuel computer regulates the fuel mixture depending on how much air is being sucked in .The 02 sensors then reads the mixture on its way out.If the mixture is is rich or lean the 02 sensors report back to the computer and tell it to adj.When a leak is present the computer thinks the engine is sucking X amount of air threw the airmass meters because the metres are telling it how much the are sucking,when in reality the engine is sucking in more [unmetered]air becuse of the leaks after the airmass sensors.The 02 sensors see that the engine is running lean and tell the computer to make the mixture richer.The computer tries to adj mixture to wear it makes sense of incoming air versus outgoing burned mixture.If it cannot adj to repair problem,it then turns on the check engine light

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AS199

This makes sense to me. I have already copied your post and faxed it to my MB tech. I will keep you posted....and, thank you again for this effort.

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Update / Check Engine Light

The 600 SEL is still with the technician. No vacuum leak(s) detected. Thus far, he is indicating that he thinks it is an electrical problem. No diagnosis yet.

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Update Again

Got the 600 SEL back from the tech today. He replaced vacuum hoses on back of each cylinder head + he found what he thought was a throttle plate that was not as tight as it should be.

I picked it up. Drove about 60 miles and this evening the check engine light is on again. It is going back to the tech in the morning. :(

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Update Again - Final?

Today the 600 SEL with the Check Engine Light problem was again picked up from the MB technician. This time, an O2 code showed itself. An O2 sensor was replaced and, the tech found what he thought was a slightly loose pin connection on the right side mass air meter.

Now, a new O2 sensor is installed with a tighter pin connection--the tech kept it for three additional days for testing. No code showed itself and no Check Engine Light came on....maybe, just maybe.....

I hope I will not have a need to post another response to this thread! Thank you to each of you for your ideas and suggestions.

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:confused: The Check Engine Light on the 600 SEL came on again yesterday. At least this time it stayed off for several days. Back to the technician this week.

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Conrad: Go back and read the 3rd paragraph of my 12/12/04 post. The light will only stay off for 4 full drive cycles when the problem is solved and the codes are erased. Your problem has yet to be identified.

You need a second opinion by someone who has the proper diagnostic equipment and a full understanding of the car. This might translate to a visit to your dealer.

How much have you spent to date? I would venture to say that it might have proven cheaper as well as faster to have it done by the dealer

__________________

New York club member since 1976.

Continuous Mercedes ownership since 1964.

1993 300SD with '99 606 engine. 111,040 miles.
1994 S350   75,238 miles
1995 S350 148,124 miles.
1996 S420 with '99 606 engine  Sold
1999 S600  one of 14 imported  Sold 
1989 Bentley 8  Sold at 40,000 miles.

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Edmond, OK
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1994 E320 Wagon
1993 600SEL

JTripp

You may be--probably are, right. I am going to give the tech the benefit of the doubt one more time---he has served and serviced this car so well thus far. One more time, then....the dealer if need be. Thank you.

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May 5, 2005. The Check Engine light is on again. Car running perfectly. Any suggestions will be welcomed.

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Mr. Conrad ----

I tried to inform you of this almost one year ago.
me-1993 600SEL with new v12(not rebuilt) new engine, all new sensors, wirings, transmission, etc, including new intake manifold MAF/MAP devices and hoses and connectors. My wife I and drive this dream machine everyday over 100 miles per day. We trade off who gets the royalty experience. We drive in - out of control Wash D.C. traffic daily. I tried to tell you what to do.
bill & monika mercer.
Falls Church, Virginia

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Bill,

Thank you for all of your suggestions---they have been much valued and appreciated. Each suggestion has been shared with the MB technician and I believe that each has been followed through. This is a frustrating issue and you are right in that it seems that once one thing is "fixed", another pops up!

Conrad

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check engine light

Hi One thing often over looked is the fuel pressure regulator on the top back of the engine,it will set off many codes but not for itself,pull the vac line off it and see if fuel comes out or it is wet.joeym

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The fuel pressure regulator has been checked and given a clean bill of health. The diagnostic code now reads an O2 sensor, the one that was not replaced earlier. So, this second O2 sensor is in the process of being replaced. I did not learn until today that it has two O2 sensors---I should have guessed as the engine in this car has two of everything! The car is to be ready in a day or two and I am hopeful that.....!

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The 600SEL is back from the MB technician, now, for about 2 weeks. No "check engine light". The second 02 sensor was replaced. The car runs perfectly, as it did before the light came on--everything checks out: no vacuum leaks, no mass air sensor issue codes, no fuel regulator problems, no electronic glitches..... My fingers are crossed and I am thinking positive thoughts.

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If it comes back on-get a new tech.He missed something.At this point you have spent more money than you have saved by not taking it to the dealer

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Two additonal starts and warm ups today. No Check Engine Light!

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Sadly, today the Check Engine Light came on at the gas station. I just filled the gas tank, started the engine, and there it was. :(

The MB technician has had ample opportunities to identify and fix the culprit(s). This week, the 600 SEL goes to the dealership. We'll see--this should be interesting, and hopefully, not too expensive.

The car continues to run perfectly.

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600 s coupe engine light

Hi,

I disconected the battery for 2 minutes and everything went back to normal.Just beware of your radio code.

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