I took my 2001 E320 to the dealer a few months ago for the Service B work and brought to their attention that my (what I believe is my) check engine icon had been on constantly for several weeks. After picking up my vehicle and asking if something related to that light was found, the service advisor sounded like he had forgotten about it and then said, "Oh, the mechanic said the light went out when he test drove it so he didn't pay any more attention to it." When I told him that the light was on when I returned to my vehicle and I had never seen the light go out in quite some time, he asked me to describe what the illuminated icon looked like. He didn't recognize my drawing of that icon with the propeller on one end so he followed me to my vehicle to see what the light looked like. He said he didn't recognize that light as one typically in a Mercedes (though that light is common in American vehicles). He said that somewhere along the line, the panel containing the warning lights must have been replaced since this icon was not typically seen in the Benz and then he said, "It must be the check engine light but don't worry about it...your vehicle seems to be performing the way it should. Just remind us to revisit the issue the next time you bring it in for work." I was not satisfied with this response and had no luck when I tried to bring it to the attention of someone of higher authority and decided to take the car to another dealership. Before being able to get another repair appointment, I took my vehicle in for its emissions inspection and it failed. The inspection tech noted the illuminated check engine light.

Around this time, I began to hear a rattle that sounded like the same rattle I heard when a piece of the catalytic converter needed to be repaired. Mercedes fixed for free as part of a previous recall that I was unaware of. I bought the vehicle pre-owned.

Three questions:

1. I'm wondering if this may have any relationship to the problem that caused the vehicle to fail emissions.
2. I was given a list of service stations that are certified emissions repair facilities. Is it okay to take it to one that can work on Merc-Benz or is it recommended to only have a Merc-Benz dealer do the repair?
3. Any idea of the general cost of this type of repair?

 

Hi,

Check Engine Light (CEL) or Malfunction Indicator Light (MIL) can have several logos. Sometimes they have words. They are Yellow (warning) in colour.
I believe your logo is the outline of an engine with a fan (propellor) on the left hand side. Correct! Why your dealer didn't know this is beyond me. Surely it is also in your handbook?

The CEL illuminates when there is an emmissions related fault. The vehicle first illuminates the CEL and if the fault become more serious (emmissions legislation is actually compromised) the engine will go into "Limp Home". Limited speed, limited gears etc.

Having the CEL on for an extended period without investigation is NOT a good idea. However....

Did the emmission station FAIL the car because the CEL was on or because it actually failed the emmissions requirement. I suspect it may be the former. i guess the regulations state that the CEL must work at startup and that it mustn't be on during the test.

Rattle from the catalyst (usually when cold) is a common problem. MB are very reluctant to respond to this issue since catalysts are expensive. A long story. The rattle is caused by the catalyst monolith bouncing around within the casing. The monolith is very brittle (ceramic) and a knock on the casing (grounding) or wading (sudden change in temp) can cause the monolith to crack and begin to disintegrate. This has the effect of reducing the monolith efficiency and can lead to emmissions test failure.
However it is more normally an annoyance since your car has 4 catalysts and closed loop emmissions feedback and unless in California your car should meet emmissions without much of a problem with some redunancy built in.
If the engine has a misfire this also can wreck the catalyst but you don't get the rattle since the catalyst is contaminated rather than broken.

Catalyst are very expensive from MB and in the UK no suitable aftermarket (cheaper) alternatives are available on some models due to low volume and difficult packaging (space) requiremments. This may be different in the USA. Even if available changing the catalyst type is not a good idea because it impacts the engine tune settings.

The small front catalyst is the most important one and when these breakup they can be ingested by the engine and wreck it. I suspect that it is your main catalyst located next to the gearbox that is the problem.

Hope this answers your questions.

Stuart

 

Sounds like the bottomline is a Catalytic Converter problem. Have them checked and replace them if necessary. One thing is for sure, if it's the Converters they won't get any better!

 

Thank you so much! Your very detailed (and very knowledgable) response is very helpful.

The emissions station did give me two failure codes. I will post the codes later; however, they also noted that the CEL light was illuminated. You are probably right that they failed the vehicle because of the light being on.

Correct---my logo is the outline of an engine with a fan (propellor) on the left hand side. I purchased the vehicle pre-owned and it didn't come with a manual (hence my reason for not consulting MB manual, though I have seen this symbol in the manuals for other vehicles in my household). The vehicle only came with one key at purchase time and I had to spring for a second key. I should have ordered a manual at the same time. The issue with the service advisor at the dealership not knowing the code was perplexing to me and was only a part of what I considered "poor customer service". I did decide to seek service at a new dealership, even though that service advisor is no longer there (and other staff who have answered the phone following his departure claimed to not be familiar with his name). Just curious...does Mercedes stick with this same symbol in their vehicles, or do they use various icons to represent the Check Engine warning? If it is the latter, just curious as to why they are not consistent with use of the code.

THANK YOU AGAIN.

 

THANK YOU AS WELL.

 

As I think I stated previously MB (and other manufacturers) do use different "icons".
For instance my S class has the words "Check Engine" which I guess isn't much use (or even acceptable in lets say France).
I suspect that legislation has dictated that in certain markets (eg USA, or even sub territories such as California) that certain icons must be used for coinsistency and intuitive understanding.
Need to wander around an MB lot to get a more definitive answer.
Stuart

 

So what were the codes that caused the CEL to be on?
You didn't state them as you indicated you would.
Stuart

 

Stuart,

Sorry for not posting the codes earlier. I took vehicle to Mercedes dealer. They replaced the mass air flow sensor (or air mass sensor?) which I'm told was related to the illuminated check engine light. My invoice stated that tech performed SDS test and found codes P0171 and P0174 in engine control module.

During the same visit, a stop lamp switch was replaced....related to the problem stated in an earlier post indicating that I could not shift my vehicle out of park after seeing the BAS, ABS, and ESP lights come on. I later learned that my brake lights were not working and, thanks to the responses on this forum, I was able to take the vehicle to the service center with some up front indication of what was wrong. (Thanks!) About 16 months ago, I had a brake lamp switch replaced. 1. Is this something different or the same as the stop lamp switch?

After driving the car home from the service center (about 15 miles) and parking it overnight, I started it the next morning and felt a hard jerk when I shifted it into Reverse. I drove it down the street for 1.5 miles and it would not go into the higher gears. I'm not sure what gear it was stuck in. So, I pulled into a parking lot and attempted to put the car in park and I could only get the car into Neutral or back in Drive. I could not put it in Reverse or Park. I put it in Neutral, put my emergency brake on and turned the car off for about 10 seconds. I then started it back up and it went into gear fine. I drove it back home without any apparent problems. I drove it about 70 miles over two days before I could get another appointment with the dealer and noticed no problems with shifting. When I did get the appointment to see if this problem was carried over from the car being stuck in Park while the brake lights were out, they checked it out and said this is a new problem and that I now need a new shifter. I am concerned that something might have causes this problem while at the dealer because I wasn't having this problem until I brought it home from being repaired for the above-mentioned items.

My right side catalytic converter was relaced at 53,000 miles and my left side catalytic converter needed to be replaced at 85,000 miles. I had bearings replaced at 53,000 miles also.

The shop also mentioned a rear seal leak.

I have been experiencing a rubbing feeling near my front tires that gets more pronounced when I slow the vehicle down. It is noticeable at slower speeds and upon initial acceleration, even without the brakes being on. Mercedes mentioned that new tires are needed and that this is possibly the cause.

I have problems with headlamp lights burning out often and the casings where the bulbs fit show some burn damage.

A few other repairs were also suggested by the service department.

Does this seem to be a lot of problems with a 2001 E320? I purchased it in 2004 with 53,000 miles on it.

Because all of the suggested repairs add up to several thousand dollars, I indicated that I am not able to take care of all of them at once. Some very hefty and necessary medical expenses have been coming out of pocket for periodic medical treatment and that is priority. I just am not able to pay for all of the auto repairs at this time. When I had the air mass sensor and stop lamp switch replaced, I told them that I could not get the rest of the work done at this time. They tried to coerce me into having more done but I said I could only authorize the two repairs. Then I drove it home and had the problem with the shifter.

I told them now that I cannot afford to get the shifter replaced at this time. After more attempted coersion, I told them I could not do it at this time. I also complained that they were now trying to charge me a couple hundred dollars for diagnostic when I was told over the phone that I would NOT be charged for them to look into the shifter problem since I experienced it right after my other repairs. They were adamant about charging me, saying they had to spend time looking into the problem, but I told them I explained to them up front that I could not afford to incur any additional charges at this time. They said they understood and would look at my car at not cost, but then said they had to charge me for diagnostics after I indicated that I could not get the new work done at this time. They told me they would have to see what would happend and that I would then have to wait until the next day to pick up my car because the tech had to "put everything back together". I am now very nervous that this incident will cause them to make some negative adjustments to my shifter so it will worsen to the point of needing to be replaced at an earlier time.

Am I being paranoid that some shops would loosen parts or make some type of adjustments to parts of the vehicle to make further repair necessary so they can make their money? I have heard this in the past and notice that more problems with my vehicle surface after I've left the shop and declined the full scale of certain other repairs. Anyone have any comments on this?

Thanks.

 

Wow!
You must have broken a mirror or similar in the not too far distant pas to be experiencing this sort of "luck".

Firstly P0171/4 means the engine was running weak. Mixture is controlled electronically. If all the sensors and components of the injection system are working correctly mixture strength is set automatically from a "fuel map" encoded in the ECU.
Although many parts can fail and give specific symptoms the key parts that control mixture and deteriorate over time are the MAF (Mass Airflow Meter) and the O2 sensors.
MAF "old age" is usually signalled by different DTC (Diagnostic Trouble Codes) but going weak is an associated symptom so I have no reason to believe that the dealer is incorrect in their diagnosis. MAF's usually give trouble at about 75/100k miles. Sometimes they can be simply cleaned but this is not MB approved for QA (Quality Assurance) reasons.

Next. 2 Brake (stop) light switche failures in 16 months is a little suspicious. Open question is what was wrong with them. Burnt contacts or physical casing damage due to incorrect fitment etc. The switch has two totally separate circuits. One works the brake lights and the auto selector lever lockout mechanism, and the other acts as a sensor for the ABS, BAS, ESP, ASR etc. This is a well known issue and if you were experiencing the symptoms (which you state you were) I guess the problem was for real.....but the question is whether you will you need yet another switch in 16months? You certainly shouldn't. I'm not actually sure if the switch has been modified, although incidence of the problem is sufficiently high that it should have been, and therefore whether the garage fitted a new or old part is relevant. Was a genuine MB replacement used?

We now come to the bit about your concern over the garage. Although some rouge traders do exist...the bottom line is so important in USA culture...that anything can happen. However I think you have to be positive and consider other possibilities.
Although the Auto selctor had given no trouble before it got locked in Park it is possible that damage was done to the mechanism by the effort used to try to get it out of Park (by yourself unwittingly). The electronic locking mechanism consists of a latch which is controlled in the shifter by an electromagnet. there was no need for the garage to disturb this mechanism. The sensor for the circuit (brake light switch) is located above the brake pedal.
If a vehicle gets locked in Park the appropriate action is to use the emergency process which requires the insertion of a pin, screwdriver etc into the hole adjacent to the Selector. This mechanically moves the lock plunger mechanically rather than electrically.

I'm sure the garage should understand if you are unable to pay at present for personal reasons since you are indicating that you will back ASAP. Why would they want to sabotage your car? I think not. However, you vehicle is a good revenue earner at present and they want to maximise the short term opportunity. NB I have nothing to do with ANY garage especially this one!

Catalytic converter replacment at 53,000 /85,000 miles is not unusual on MB and most other luxury cars at this sort of mileage due to monolith breakup.
Bearing (ENGINE? replacement at 53,000 miles is most worrying. WHY?
However if it was the suspension bearing due to water ingress than this is pretty typical for a a car 5 years old or so.

Finally, Mercedes mentioned that new tires are needed. Without experiencing your noise it is difficult to be definitive. However the MB diagnosis is not unreasonable. Anyway if you need new tyres due to wear you will be able to see if the problem goes when they are changed, so long as the garage has confirmed that there is nothing wrong with the suspension and brakes for safety reasons.

In summary, the nature of problems experienced on cars is changing. Whereas it used to be things like no start, oil leakage, water ingress etc, nowadays its nearly always associated with electronics. The higher the spec of the car the more there is to go wrong.
MB have led the way with advanced electronic systems like ABS, ASR, BAS, ESP, Electronic Injection etc. and now they are moving to brake by wire, auto cruise (radar), etc. Most of these systems are for your safety and work entirely in the background.
Unfortunately this technology has had to mature and MB have paid a price for this.
Although MB are no longer where they used to be for reliabilty (JDPowers) the sorts of problems experienced are endemic to most modern cars including those at the top of the list.

Hope this is useful,
Stuart