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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
     
    Jim2 likes this.
  2. Wighty

    Wighty Senior Member

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    Was it an MB specialist with Star diagnostics buddy ?
     
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  3. Wighty

    Wighty Senior Member

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    Your Mercedes:
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    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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    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:
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    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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    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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  12. OP
    Simon G

    Simon G Member

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    Hi all

    Just an update on this situation, which unfortunately is not resolved .....

    I took the car to Star Tech in Poole who were very helpful and confirmed the EGR valve needed replacing. They ordered one from Mercedes but were told that neither Mercedes UK or Germany had any in stock and that dealers had back orders since June !!

    Star Tech were reluctant to fit an OEM version so I made enquires with another garage who said they could source one next day, so I asked Star Tech to cancel the order and took the car to the other garage. Unfortunately, they called this morning to say that their supplier had let them down and could not supply a replacement EGR valve either - Wonderful :(

    I called Mercedes (Poole) directly to confirm the situation and they confirmed that there were significant back-orders and they could not confirm when one would be available - I really can't believe that some customers have been waiting since June for such a critical part !

    The situation has been ongoing for 3 weeks now and I've been avoiding driving the car (which is in permanent limp-mode) where possible, but my job is sales and there's only so much you can do by phone so the situation's far from ideal.

    The new garage suggested doing an EGR remap as a temporary solution which I reluctantly agreed to as I need the car working for Xmas and this was done today.
    However, even though the car is not running in limp mode and no codes are showing it just doesn't feel right with erratic gear changes and hesitation / stuttering on acceleration which was how the issue originally started before it though up P0404 & P0405 codes

    I did a quick OBD scan when I got home and I'm waiting for the garage to call me back but now feel I'm back to square one and wondering if the EGR valve codes were just a red herring and that there's some other issue thats not showing a code
     
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  13. bembo449

    bembo449 Senior Member

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    This sounds like a real pita especially if a recommended indy cant find the real fault pal
     
  14. OP
    Simon G

    Simon G Member

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    Just wondering if there's a physical issue with the EGR causing it to be stuck, and that removing the EGR in the map is now just masking the issue and stopping the car going into limp mode and that now I just seeing poor running due to EGR issues ?

    Back to the garage we go :(
     
  15. OP
    Simon G

    Simon G Member

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    Hi All

    I just wanted to give you an update on the issues Ive had with my car, as they're ongoing and becoming more perplexing ..... Sorry, it's a bit long ...

    After having the EGR mapped out the car still didn't feel right with rough gear changes and the engine noisier than normal at >1500rpm.

    To make matters worse, long trips turn into a nightmare where the original symptoms would come back after between 1.5 to 2hr of motorway driving, i.e. holding gears until 3k rpm, changing down too early, engine sounding much noisier and no power. Stopping and restarting the car for a period of time sometimes fixed it for another couple of hours.

    I took the car back to Star-Tech (Who've been very helpful and highly recommended) and they checked it on their computer and took the car for a test drive, but they were unable to see any stored codes and even though I could detect the gear changes not being as smooth as before, their mechanic couldn't .... but I guess I know how the car feels better after 25k miles.
    They suggested that the other garage who mapped out the EGR should have blanked off the EGR. If they hadn't and the valve was stuck partially open or closed it could cause the issue.

    They recommended another garage who could blank the port so I arrange to take the car to them.
    The night before it was due to go it the engine check light come on and I had another new codes stored, which was a P062F which appeared to relate to an Engine Control Module - EEPROM error.
    I following morning I took it to the garage to have the port blanked and the engine check light was still on - I explained the code and this re-enforced the suspicion that the EGR map may not have been done properly and they may just have disabled to fault code, confusing the computer.

    They agreed to do some investigation and blank the EGR port and they called me back a few hours later to say a) there was no engine check light on and no stored codes (they were there the day before!?) and that on checking the EGR map they spotted some very off values and data deleted that should not have been.
    They recommended they restore everything to default and map the EGR out again but the cost for doing this would be the same as a full performance re-map ......... I was reluctant to do this before I knew the original issue had been resolved, but I agreed on the basis that they waived the original cost for blanking the EGR port in the hope that it would finally rule out the EGR as the culprit.

    I picked the car up the next day and they said everything had gone well and the car was running perfectly. The drive home was certainly smooth and the engine noticeably quieter so I was confident that the issue had been resolved.

    The next day I had a 300 mile round trip to make, and for the first 20 miles all was well and the car felt like it used to - Smooth and quite. However, the engine check light came on again :(
    The car was still running perfectly so I continued with my journey.

    After approx 2hr of motorway driving I encountered a traffic jam and as I slowed down the car did it's old thing of changing down too early, the engine noise increased significantly and it started holding gears until 3k-rpm and lack of power :(
    I pulled into services, connected my OBD2 scanner and had another two new codes, this time a P2002 (Particulate Trap, Bank 1 - Efficiency Below Threshold) and a P1297 (Status pending - Injector High Sides Shorted Together)

    On my return trip the same thing happened again ; Car running OK (But not as smooth or quiet as when I initially set-off) and after 1.5 hours the car started holding gears until 3k rpm, changing down too soon and engine was noisy. I also noticed that if I cruised along at a constant 60 mph that I could feel the car pulsing, best described as as a very slight surge followed by the feeling of being held back and I could see the revs going up and down slightly when doing this. I connected the OBD scanner and monitored the RPM's over a 5 mile distance and they were constantly chsnging between 2,450 rpm and 2,350 rpm ..... not much, but enough to feel.

    I stopped at services about 1 miles from home and when I re-started the car everything was fine again, very smooth and quiet and monitoring the RPM's this time showed a perfectly flat smooth line.

    The garages are at a loss to explain what's going on and its odd that I have the exact same symptoms today that I had nearly 2 months ago, but I'm getting different codes displayed.
    The issue is compounded but the fact that the major issue of holding revs and going into what feels like limp mode only happens after 1.5 to 2hrs of high speed driving, so difficult for the garage to replicate. However, I'm at a loss why their Star diagnostics isn't able to see anything and when a code does appear that it's different.

    Anyone come across similar symptoms ?
     
    Last edited: Jan 16, 2020 at 8:26 PM
  16. LostKiwi

    LostKiwi Senior Member

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    First thing I'd do us get them to remove the map, reinstate to factory and find the original issue. You're now in a state where so much has been changed you don't know which piece of work is doing what. Far too many variables and a non standard configuration will make this more difficult than it should be.
     
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  17. OP
    Simon G

    Simon G Member

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    Thank LostKiwi ... and apologies for the appalling grammar and spelling mistakes in my last post (hopefully now more all corrected)

    I think you may be right as I seem to be digging myself into a deeper hole.

    It’s going back into the mapping company for them to have a look on Monday, so if they can’t find anything obvious I think I’ll ask them to restore back to factory settings, re-enable to EGR and unblinking the port.

    However, 2 garages diagnosed the issue as the EGR valve being faulty which is why it’s so confusing to have the same symptoms with the EGR being completely disabled.

    I need to drive around 700 miles next week for work so a little concerned are the moment
     
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  18. LostKiwi

    LostKiwi Senior Member

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  19. Wighty

    Wighty Senior Member

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    Good luck , and let us know how you get on
     
  20. OP
    Simon G

    Simon G Member

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    Out of interest, could a clogged DPF or faulty DPF sensor cause the symptoms I’m experiencing ?; engine noisier, lack of power, erratic gear changes at low speeds, EGR fault codes & RPM surging at motorway speed
     

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