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Clk200K high CO2 and P170 code.

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by Ryannn, Jun 6, 2018.

  1. Ryannn

    Ryannn New Member

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    Joined:
    Jul 1, 2017
    Your Mercedes:
    C209 CLK200 2005
    Hi everyone,
    Hoping someone can help me with a diagnosis.

    Had an EML come up on my 2005 CLK 200 recently. Read the code with my cheap reader and it’s showing 2 codes, “NA” and “P170”.

    Took the car for MOT today and it’s failed on CO2 emissions at 2%, all the rest were fine.

    Any ideas where I should be troubleshooting? Car’s been fault free for over a year!
     
  2. John Laidlaw

    John Laidlaw Senior Member

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    Location:
    Wirral
    Your Mercedes:
    W212 E63 ///AMG V8 Biturbo Volvo XC90 2018
    Fuel and air ratio must be off- timing or maybe spark plugs or leads is where I’d start I guess, but your codes don’t mean anything you can work on, so best get a diagnostic with a Star machine at a Mercedes Independant
     
  3. Oldspanners

    Oldspanners Senior Member

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    Oct 30, 2017
    Your Mercedes:
    C CLASS 2004 C180
    I had the same codes.
    Turned out to be firstly the after cat O2 sensor faulty and oil leaking from the cam magnets into the wiring harness.
    A good place to start, other than obviously getting a Star diagnostic, is to disconnect the after cat O2 sensor below the car and look for signs of oil contamination as it's the lowest point. There may also be signs of oil at the engine ECU connector.
    If this is your problem it's all easy enough to fix for the DIY mechanic.
     
  4. OP
    Ryannn

    Ryannn New Member

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    Joined:
    Jul 1, 2017
    Your Mercedes:
    C209 CLK200 2005
    Cheers for the replies. I had the oil contamination in my old CLK but it got written off before I could fix it!
     
  5. OP
    Ryannn

    Ryannn New Member

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    Your Mercedes:
    C209 CLK200 2005
    Ok, I have an update!

    Took to an MB specialist for diagnostics. No faults found other than the pre cat Lambda reading high. They had a good look round for vac leaks but couldn’t find anything. So suggested next step is to change the sensor and take it back...

    The plug for the pre cat Lambda is buried behind the engine, what’s the best way to get to it?
     
  6. Oldspanners

    Oldspanners Senior Member

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    Your Mercedes:
    C CLASS 2004 C180
    If it's the same as the C class it's on the left hands side of the gearbox mounted in a plastic clip. Access from below the car after removing the rear plastic under-tray. Tie a piece of cord to the end as you remove it as it makes it a lot easier to pull the new one in over and around the back of the engine and bell housing.
     

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