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2011 CLS350 Gearbox Issues & not recording fault codes

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by Simon G, Dec 1, 2019.

  1. Simon G

    Simon G Member

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    Hi all

    I’ve owned a 2011 Merc CLS350 CDi for 12 months and its been one of the best cars I’ve owned.
    The cars done 78k miles (58k when I bought it a year ago) and it has full Merv service history with the last service carried out by a the dealer in July this year.

    Over the past week the cars been behaving strangely with a couple of intermittent issues, one I can live with but the other more serious.

    The first issue is occasional rough staring from cold - I always wait until the glow plug light goes out, but about 1 in 10 times it seems to struggle and turns the engine over 5 or 6 times before starting.

    The second issue is more serious as its gearbox related ...... Initially the car drives fine, but gradually the gear changes seem to become a little less smooth and after a number of miles (10 yesterday) the car will hold each gear change until 3,000 RPM and downshift abruptly. When this occurs the car won’t exceed 3,000rpm and flooring the accelerator results in very little happening so I assume it’s in limp mode.

    No engine check lights or messages are shown on the dash with either issue.

    I took it to a local specialist for them to diagnose the issue they were very surprised that there were absolutely no error codes stored in the car - they commented that this was very unusual as normally there would be some historical codes.
    When the car was with them they test drove it for about 5 miles and didn’t experience any issues - they flashed the gearbox with new software just in case.

    Yesterday I drove the car for 10 miles and the gearbox issue occurred again but this time the engine check light was on - this was good news as I thought that this would help them diagnose the issue.
    However, after stopping for a break and setting off again the engine check light had gone out and the car was driving almost normally (gear changes still not as smooth as before) so I’m not sure if any codes will be stored for them to check

    Has anyone experienced a car thats not saving fault codes and/experienced similar gearbox issues?
    Many thanks
     
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  2. Wighty

    Wighty Senior Member

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    Your Mercedes:
    W211/E320cdi/2009 and CLK200k 2009
    Was it an MB specialist with Star diagnostics buddy ?
     
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  3. Wighty

    Wighty Senior Member

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    Your Mercedes:
    W211/E320cdi/2009 and CLK200k 2009
    Other thoughts are , is the car due (another) an ATF and filter change on the gearbox at that mileage ?
    The slow start could be Glow Plug Relay (£130ish ) easy replacement and a consumable part .
    Lot of guesswork without proper MB diagnostics though
    How old is your cars battery , date is stamped on a terminal post
     
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  4. OP
    Simon G

    Simon G Member

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    Hi, yes - the company was Star-Tech in Poole who came recommended
     
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  5. OP
    Simon G

    Simon G Member

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    hi, according to the service history the ATF & filter were changed in 2017 and I believe only needed every 4-5 years so Star-Tech don’t believe that’s the issue.
    Not sure on age of battery, so I’ll check.
     
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  6. Wighty

    Wighty Senior Member

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    Your Mercedes:
    W211/E320cdi/2009 and CLK200k 2009
    It’s a tough one , because if a reputable/knowledgeable MB specialist is involved that rules all us out :D
     
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  7. LostKiwi

    LostKiwi Senior Member

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    Your Mercedes:
    '93 500SL-32, '01 W210 Estate E240, 02 R230 SL500 (Malcolm Spec), 04 Smart Roadster Coupe
    If it's dropping into limp mode there must be codes getting logged. You may need to get it read 'in the act' so to speak.
     
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  8. malcolm210

    malcolm210 Senior Member

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    If it’s the original battery I would certainly change it before spending any more money and time on the car, modern car electrics don’t like an old/under voltage battery. The gearbox symptoms are certainly puzzling it might be the speed sensor in the gearbox starting to play-up with it holding onto gears but without codes it’s a guessing game.

    As a matter of interest when did the car last do a DPF regeneration although I would imagine a blocked filter would bring on the engine management light permanently
     
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  9. alexanderfoti

    alexanderfoti MBO Forum Supporter Authorised Forum Supporter

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    Your Mercedes:
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    Yes I have had a few that drop into limp mode and then fail to store any historical codes.

    I suspect your vgs module Is loosing comms. Although the check engine light should now have logged a fault. I imagine this code will be "no coms with transmission module".

    You have to read the module whilst the fault is happening unfortunately.
     
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  10. OP
    Simon G

    Simon G Member

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    Thanks guys

    I’m calling Star-Tech again tomorrow to very the car booked in.
    I may have to drive the car for a few miles to get the fault to re-occur before I drop it down to them.

    I‘ll let you know the outcome
    Cheers

    Simon G
     
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  11. OP
    Simon G

    Simon G Member

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    Cars going in tomorrow, but I decided to buy a cheap OBD2 diagnostic tool and it’s showing the following code;

    P0405 EGR Sensor A Circuit Low

    ... looks like it may be nothing to do with the gearbox after all, but just going into limp mode
     
    Last edited: Dec 2, 2019
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