Hi, I have E200 K 2001 sedan.EMS light came on at 104000 Kms. Changed MAF meter and sensor as well as check valve.Lihgt comes back in 2 days.Reset agian by garage,comes again in 2 days.It is persistently on now.Have spent so much money to no vail. Please someone help.
bonedoc

 

Hi,
The first thing you need to do is to get the Diagnostic Codes read.
In the USA this can be done for free at many garages.
Once you have the coide come back and we will advise what the code means and what needs to be done.
Stuart.

 

Concur. Obtaining the error codes is everything and of course clearing the error codes after replacing/repairing the actual and real problem item or device. Let us know the what the diagnostic error codes readings are andwhat your garage that obtained theerror codes NOW saysneeds tobe done. thanks

 

There are several reasons MAF Sensor can set a code. Let me take a guess...Code *P0170 or *P0173 Self-Adaptation out-of-range. Usually, this means that either the engine is either too lean or too rich. These values can ONLY be check using an SDS (Star Diagnosis), and not any scanner (e.g. Snap-On Tool, or Any Scanner). That's the advantage of having an SDS...like me!!! :&gt Anyhow, I strongly doubt that a garage or a gas station in either U.S. or U.K. would have such a Diagnostic Tool. Because first, you have to have worked at a dealership for quite some time to be able to navigate through this system. Okay, going back to your question...

Here are several possibilities: First is Mass Air Flow Sensor, which after replacement should be reset through Control Unit Adaptations (Throttle Valve Angle, Zeroing out the previous actual values, etc.). Second, a dirty Air Filter can cause it as well. Third, low fuel pressure causing incorrectair/fuel mixture ratio readings from Oxygen Sensors. Fourth, cracked Intake Hose causing vacuum leak. These are some possibilities that you might want to get checked. Wish I was in Dublin...I'd like to visit there one of these days.

take care,
-mar-

 

Hi,
I hate to disagree with you BUT OBDII DTC's (On Board Diagnostic Codes) can be read by ANY OBDII compliant scan tool. Its an International Standard.

Navigate through the system. You plug into the 16 pin OBDII port, turn on the ignition, and any codes (pending or stored) are displayed. It so simple that this is why SOME garages. especially in the USA. will scan the OBD and tell you what codes are set in order to get the repair job. It literally takes 2 minutes.

P0170/P0173 is the classic SIGNATURE of a faulty MAF. Codes do not tell you what needs to be done to rectify a problem. The code tells you what ECU parameter is wrong.

You refer to Self Adaptation...this is an MB term...more commonly known as Fuel Trim. The STFT Short Term Fuel Trim advises how much away from IDEAL (in % terms) the real time fuel mixture is.
The LTFT Long Term Fuel trim is the "self adaptaton" value which is basically a start up offeset or baseline correction. The value of STFT and LTFT can be determined with any OBD compliant scanner with REAL TIME DATA CAPABILITY.

I use a DynoScan (from Auterra.com). Cost me 150 USD and runs on my Palm PDA. very handy. No power leads etc and has been rock solid for the last 4 to 5 years. Many other manufacturers make such equipment for similar price. Most run on a PC laptop.

The P0170/3 signature usually points to a dirty or bad MAF and the sensor needs to ber cleaned or replaced. Its the MAF sensor that causes the fuel trim to be wrong rather than the other way around.

Yes dirty air filter, bad O2 sensors etc can also cause similar incorrect "Adaptation" values but these do not give the P0170/3 code signature.

Although I have no MB specific training Bosch Electronic Injection system (as used by MB) is used by many manufacturers...or at least extremely similar concept.

Hope this helps.

As I stated previously. GET THE CODES READ and come back.

I suspect you will find a P03XX code showing (Misfire) however there are many other possibilities. If you have a P03XX code the first thing to do is to check the plugs and leads.
If you have a P0301 (Cyl 1 misfire) swap the plug and lead with lets say No 4. Does the problem move? i.e. the code becomes P0304. If so you know its the lead or plug causing the problem. If not then need to do similar with injector. If many cylinder misfire on just one bank (assume V6/8) then the O2 values and possible codes are important.................

Incidentally plugs should be chhanged circa 75/100k dependent upon engine type etc.

 

I have three OBD II Scanners...one is Snap-On 7.4 ($6,500)...second is OTC Scanner ($1,500), another Generic Scanner ($100), whichis the same as what Auto Zone to use to check codes, and I use this $100 Scanner for my CODE READINESS. That's the reason why your Check Engine Light keeps coming back because every time someone resets the codes, it erases ALL the "Code Readiness" Monitor, andyou havetodriveitforseveral milesand go through aDrive Cycle.Hmmmmm...Using the SDS (Star Diagnosis) gives so much access (e.g. programming Instrument Cluster (e.g. mileage), Programming ME-SFI, ETC, PSE, SAM's, Telematics,....etc...name it...I can do it using SDS. Something Snap-On or other Generic Scanners can't do. However, there's Auto-Logic, which is usually mostly European cars, but you have VERY limited access. It was really design for (BM-Trouble-U's) another short name for BMW. TRUST ME ON THIS...SDS is the BOMB!!! Dirty Airfilter can give *P0173 and *P0170 codes. If the MAF Sensor is not receiving the correct volume of air passing through the MAF sensor...this will through off you readings. Trust me, I see it when Techs replace Air Filters all the time and not clean the Airfilter housing, the next day Check Engine Light comes back with MAF Sensor coding. These are advice I give you guys...take it for what its worth. Also, there is a TSB (Technical Service Bulletin) for quite some time now....probably when they started building the 112 and 113 Engines, which was 1998.

take care,
-mar-

 

Hi mar,

I'm always willing to learn and sense that you may have valuable input especially with your MB credentials. However I cannot agree with your post.

SDS Star is undoubtedly the very best diagnostic tool on an MB. After all it is the MB approved equipment. However thanks to OBDII (circa 1998) engine management codes were standarised and can be read by any OBDII compliant scanner.

What many OBDII scanners CANNOT DO is to access the body and chassis ECU codes, live data and activation routines, and in particular the Instrument pack for mileage "adjustment" etc. For this you need SDS / Autotech etc which is mega EXPENSIVE equipment. I would love to have SDS kit!

However we were talking ENGINE/TRANS codes which are OBDII compliant (by law). You do not need SDS to read these. Try http://www.auterraweb.com/dynokitsnohotsync.html

I also note your statement...
If the MAF Sensor is not receiving the correct volume of air passing through the MAF sensor...this will through off you readings.

The MAF measures air flow (Mass Air Flow) so if it is working correctly it will measure the flow of air. However IF the air flow is SEVERELY restricted the flow of air over the sensor is impacted turbulence / non laminar flow) and this may impact readings.

Trust me, I see it when Techs replace Air Filters all the time and not clean the Airfilter housing, the next day Check Engine Light comes back with MAF Sensor coding.

I find it difficult to understand how an air cleaner HOUSING can get that dirty. The filter YES.
My 130k M112 air cleaner is "as new" both outside and inside.

Returning to BONEDOCS problem. He replaced the MAF without determining what codes (if any) had been set. MAFs do give problems at circa 75k + miles but many other things can cause the CEL to illuminate. It is always good diagnostic practice to be able to turn the problem ON / OFF. Only then can you be sure that you have identified the real issue.

In addition it is also important to ensure that normal routine maintenance / service is up to date prior to embarking on changing parts without adequate diagnosis / analysis.

Lets wait and see what codes are pending / stored.

Stuart

 

Let's wait and see which codes he has, and we'll perform process of elimination...

take care,
-mar-

 

I agree that you can check codes with any scanner. My $100 scanner can do it, but I'm very limited as far as pinpointing what the problem is.

take care,
-mar-

 

Hi All,
Thanx a lot for the inerest in the topic.Just to set the record straight....Engine light came on at 104000 kms(E200 Komp 2001 model).Went to local garage....checked the code...it was....P2036..Intake air device,wrong operation,air entry too small....that was exactly what computer read....he changed MAF and reset.....light back on in 2 days...reset again...still bright as sunshine....please help.look farward to solution.

Thanx.
bonedoc
dublin.