Exhaust related error codes - help required please

Discussion in 'Engine' started by tordofm, Jul 30, 2009.

  1. tordofm

    tordofm New Member

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    c220cdi w203 est, command, elec climate, parking sensors, leather, BT phone, heated seats, auto L&W
    Hi, I am a newbie to fault diagnosis so require a little help. I have a late 04 w203 c220cdi and the EML came on last week. I just purchased a cable and have plugged it in and I got the following back from my software:

    P0426 Catalyst Temperature Sensor Range / Performance
    P2084 Exhaust Gas Temperature Sensor Circuit Range / Performance

    So my logic says that I should find out if the above codes come from the same sensor or two different sensors, which is where I need some help. If two different then it is not a sensor problem but could be more serious.

    One observation is that when driving I notice that the drivers console side footwell gets warm and I assume that this is where the exhaust passes which may indicate that it is not a sensor problem.

    Any help or next step suggestions would be much appreciated.

    Marc
     
  2. lynall

    lynall MB Enthusiast

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    Does your code reader show live data ie what the sensors are showing with the engine running?
    If so you can monitor the sensors perfomance and try to suss out whats wrong, if its just a code reader it wont do this.
    What reader have you got?
    Couple on here have the U581 quite good.



    Lynall
     
  3. OP
    OP
    tordofm

    tordofm New Member

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    Hi,

    My code reader is a laptop with scantool.net running on it. It does allow me to read live data and from memory I did see some temperature sensors showing around 160oC from the exhaust (I will check again), I am not sure if this is accpetable or not. I have now cleared the codes and the EML and after 40 miles the codes have not returned and the EML is still off. When the codes first showed up it was as soon as I started the car from cold. If I could find out what sensors are throwing up the codes I could then try and find out what the operating ranges are!

    Thanks

    Marc
     
  4. lynall

    lynall MB Enthusiast

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    Try a search on here for c220 cdi egr fault i remember reading something a while ago, was causing drivability problems etc.

    The fact its got a temp sensor in the exhaust reminds me of a particulate trap as opposed to a cat, when engine up to temp and it decides it needs to clean the trap it raises the ex gas temp to burn the rubbish off.

    Maybe do a google i could and am probably wrong!



    Lynall
     
    Last edited: Jul 31, 2009
  5. lynall

    lynall MB Enthusiast

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    Come across this today may give you an idea.

    A particulate trap does exactly what its name suggests: it traps particulates. A fine honeycomb silicon carbide material captures the particulates in cells to prevent their release into the atmosphere. Half the cells are blocked at one end so the exhaust gases are forced into the open cells and through the porous cell walls. Particulates are trapped in the cells and the exhaust gases flow out the end of the other half of the cells to the tailpipe. In simple terms, the particulate trap is just a very sophisticated filter. The cell material is coated in precious metals such as Platinum and Pallidium to help burn the particulates when the particulate trap needs to be regenerated.
    Over time, the cells in the particulate trap become loaded up and exhaust gas flow through the trap is restricted. Temperature and pressure sensors on the exhaust system monitor the efficiency of the trap. When the engine computer determines that the trap needs to be cleaned, it will operate the engine to burn off the carbon particles in the trap. That’s when things start to heat up.
    To clean out the particulate trap, internal temperatures must climb above 500 C. this is much hotter than normal exhaust, so a Diesel Oxidation Converter (DOC) mounted in the exhaust system in front of the particulate trap provides much of the heat. The computer will modify fuel delivery, injection timing, turbocharger operation and even throttle position (yes, some systems will use an electronic throttle specifically for cleaning the particulate trap) to create heat in the Diesel Oxidation Converter. The exhaust gases are heated by the catalytic operation of the DOC and then flow into the particulate trap where the catalytic operation of the trap burns out the soot. This can take several minutes to accomplish, and will typically be done while the vehicle is driving down the highway.



    Lynall
     
  6. OP
    OP
    tordofm

    tordofm New Member

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    Wow now that is one clever system and could well explain why the sensor was triggered but the fault has not come back. I am going to keep an eye on the exhaust temperatures over the coming weeks via the laptop and see if I spot any changes. Let's hope it was a one off but if it changes I will update this post.

    Thanks v much for taking the time to respond, much appreciated. I noticed you were also in Kent.

    Marc
     
  7. lynall

    lynall MB Enthusiast

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    Yep in Maidstone dont know why but i had it in my mind you came from Norwich:)

    Ps im not sure your car even has this type of set up, just guessing because of the temp sensor.

    Trucks at work have them but thats because of the adblue set up which is the next step up from the particle trap, any new diesel car/van with the word blu/blue in its title almost certainly has the same adblue set up ie bluefficeincy, bluemotion.

    Meant to say some of the older trucks that were retroffited with particulate traps could be removed and steam cleaned out.




    Lynall
     
  8. BlackC55

    BlackC55 Authorised Forum Sponsor Authorised Forum Sponsor

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    It needs to go on a star and have the soot burned off using one of the menus.
     
  9. OP
    OP
    tordofm

    tordofm New Member

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    Thanks BlackC55 for the suggestion. I did notice after a 100 mile journey this morning that the exhaust was pretty hot and it had a funny smell.

    lynall out of interest can you recommend any good independant merc mechanics in the kent area as mine has just let me down.

    Marc
     
  10. lynall

    lynall MB Enthusiast

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    No sorry i cant as im tight and do everything myself:D

    Apparently there is a fella called Steve in the Maidstone area whos meant to be good but you have to text him and he will reply, no number im afraid but a search may reveal it on here or just post up asking for his number.



    Lynall
     
  11. OP
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    tordofm

    tordofm New Member

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    Thanks again Lynall. After a quick search Steve at Wingham near Canterbury is the man and he certainly has a lot of glowing references.

    Marc
     
  12. TChuma

    TChuma New Member

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    Hello. I am new to this site and hope that I can tap into your wisdom regarding some stored fault code on my C220 CDI. Its code P2084 Diesel particulate filter. Flow monitoring of air mass. The air mass is too small.

    The above seems to suggest that Diesel Particulate Filter is faulty and might need replacing. I guess this is so because the self-cleaning mechanisms have now failed. That being the case the sensors are reading that the airflow is too small.

    However, I have recently taken the car to a Merc main dealer; they suggest replacing both tempertaure sensors at a cost of north of £400, including labour. I thought they may be over-selling; only one sensor may be faulty, if at all. I then got a second opinion from an Alternative Merc repairer, who suggested replacing one sensor for £130 plus labour. Merc main dealer qouted each sensor at £66 + vat, he he he! Who is fooling who?

    Now then, I am getting the sense that I am probably better off going DIY, so I would like to know how easy this would be; to replace the sensor(s) myself. I have some experience of using tools, but not on this system.

    Since the second opinion backed the need to replace the sensors, I am almost persuaded that the diagnosis is correct. What is your opinion?

    Regards
     
  13. OP
    OP
    tordofm

    tordofm New Member

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    c220cdi w203 est, command, elec climate, parking sensors, leather, BT phone, heated seats, auto L&W
    Hi,

    Mine turned out to be an exhaust sensor. To diagnose it I purchased a cheap cable and diagnostic software from eBay. This showed that whilst cold one exhaust sensor was showing 90 degrees centigrade and the other was around normal air temperature. A friend of mine changed it for me but it looked as simple as one spanner and a connector so I would definitly do a DIY job on it. The most difficult thing is to figure out which one of the two DPF sensors are at fault, you should be able to do this with the eBay cable / sw.

    Good luck

    Marc
     
  14. Dean Fletcher

    Dean Fletcher New Member

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    Mercedes E250 CDI Coupe
    Hi my car is going through the same thing did you get yours sorted. Thanks
     

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