Scirocco Central

Dear All,
I am looking for some help with the above but my problem is a bit different to most I think!
I have had my 2.0 TDI 170bhp for some ten years now ( love it) but only use it occasionally since retiring (it spend most of its time garaged). Therefore it has just reached 18k yesterday.
Over the last couple of years I have had increasing occasions when it has gone into limp mode when on a long run. (seems worse since having the emissions scandal adjustments!).
Now if it stands for a week or so in the garage it is often difficult to start unless the battery is fully charged ( battery is relatively new as well). When this happens I get the EFR fault code displayed on the display until I get it started.
Once started and used it starts fine on each occasion after that until again parked up for a week or so!
I have just returned from a weekend away having travelled a long distance and it went into Limp Mode 10 times during the outwards and return journeys - I now really have to try and sort this out before my wife makes me sell it or some HGV flattens me when I cant overtake as the speed plummets in limp mode!!!.
The codes I get are:-
P0234 Engine Overboost Condition
00564 Selector Lever (E313) -Static - No define
01314 - 052 Engine Control Module - Sporadic 004 - No signal/Communications.
The above to me would indicate a sticky carboned up turbo and /or an actuation problem with the selector lever and if the car had a 100K or did any slow short journeys I would have expected that but at 18k and only long journeys taken I would like to ask anyone with more experince of such problems for their views on both the overboost and the difficult start on a car that stands for long periods which I think are both linked somehow? (I did try an in-tank EGR/Turbo cleaner and a spray in version also a few months ago but they don't seem to have cured the situation either)
The only other thing I have noticed is that after starting , even when not in limp mode, and when the car is in neutral if I depress the accelerator the engine wont rise above 2000rpm but this could be a "governor" situation peculiar to VWs to protect the engine - Can anyone explain this to me as well?
Any help or even ideas would be greatly appreciated.

Quite surprised at getting some 284 reads to not get a single reply, comment or idea given the common happening of "limp mode" from overboost. Well, after a lot of investigation I think it is almost certainly a carboned up turbo so may need to remove it to clean.
I managed to find a way to do a "Mr Muscle clean" of the turbo (that I have not seen done before) without removing any significant components but even this hasn't cleared the problem. So now I am asking if anyone has seen a video or manual download to show how to remove this turbo?.
The turbo is very visible and accessible at the top back of the engine so I wonder if it is a straightforward removal from the top or whether there are unseen problems to face?
Any help on this would be very gratefully received

Three months on and still cant get rid of the fall into limp mode if I go above 4200rpm. At 18k miles still cant see it being a coked up turbo but I get ever closer to having to take it off to see! Last tryouts today are to remove and clean the G31 sensor as that can be implicated in a P0234 fault according to VCDS guidance from Ross.
Does anyone know where the G31 is located on the 2.0 TDI 170hp model? ( I cant find any photo or diagram showing the location of it on this model - plenty for other models or Audis).
Many thanks for any assistance.
John

Personally id start by testing the N75 valve as its probably the cheapest and easiest fix. A leak in the wastegate actuator signal hose (coming from the N75) would definitely make you overboost. If all the readings from the n75 valve are correct id turn my attention to a stuck shut wastegate but i highly doubt it since youve only done 18k miles. Also the turbo and the exhaust manifold are one piece (correct me if im wrong) so youd have to remove the exhaust manifold to remove the turbo which is pretty straight forward however quite fiddly.

Probably not what you were looking for but i guess its better than nothing [emoji2375]



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Thank you for the reply and ideas - much appreciated as not a single other soul replied even though it had lots of views logged..
Well after a solid further week of diagnostics using VCDS, vacuum gauge, endoscopic camera (to view inside the turbo) plus some novel tricks to ensure the actuator arm and actuator rod itself were all working faultlessly I think I have finally cracked it ( hopefully!).
Although the boost is high at max revs ( 2600 mbar) the problem appears to come from a dirty MAF sensor which was feeding the wrong data to the ECU resulting in a too low predicted Boost. The limp mode was resulting from too big a difference between predicted and actual boost. I tested and logged a hard run yesterday and a 30 min very hard run today and not a hint of limp mode even at red line rpm in most gears and most of that uphill under load.
I never even suspected the MAF/MAP sensor as the cause as no one flagged that up as a possibility.
Fingers crossed I can now get back to enjoying the car.

Well two years later I am still suffering the same limp mode, but not as often. During that time I have replaced MAF twice, cleaned N75 and then later replaced with new N75. Done all vacuum checks several times and made lots of checks with VCDS but never yet found a faulty component or out of range value!!!
In desperation I recently went to a guy recommended for his VW knowledge but having heard what I had already done ( and the fact I still only have 20K on the clock) he said it could be a pinhole leak in the wastegate actuator diaphragm. So I have been checking this again for vacuum loss but can find none.
HOWEVER for the first time I decided to measure the voltages coming out of the wastegate sensor on top of the wastegate itself. With no vacuum pulled the sensor should show 4 volts (I have been informed ) and with full vacuum pulled it should be 0.76 volts. When I did these measurements with multimeter I only get 2 volts (no vacuum) and 0.78 volts (full vacuum)!! Suspecting I may be doing something wrong I ran the VCDS test for this and that confirmed the readings I got via multimeter.
Has anyone else ever found a reading as low as 2 volts on the wastegate sensor? This may be the breakthough I have been looking for all this time so any commenst or thoughts would be very welcome.
regards
John

Should be between 0.65 ... 0.85 and 3.30 ... 3.90 V.
But also good to check if the mechanism isn’t stuck.

Thanks for the comments.
Will look further into this and post what I find as it may help others.
I wondered if some wastegates had a lower voltage than 4 volts but nothing seems to indicate that in all I have read. The engine is the 2.0 tdi 170 bhp CBBB model)
It can only be a stuck or failed sensor, wrongly adjusted wastegate nuts (never been altered from new) or the wastegate not closing properly I think.
At least it gives me a target to aim for but any other thoughts on this very welcome
John

The vgt actuator position sensor is almost all the same across different VAG 2.0 tdi engines.
You can find a lot about it on youtube.
If the actuator or sensor is broken you can replace it seperately no need to change out whole turbo.
Just look for Borg Warner 2.0 tdi turbo actuator and check if it's suitable for your engine code.

See page 205 in this workshop manual.

https://www.dropbox.com/sh/nerw5cwkh9ug ... EA189).pdf

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Thanks for the info. I have that Service Manual but not seen that youtube video.
A bit more work this morning revelealed that the actuator rod begins to move at 11 ins vacuum (and not 3-5 as it should) and stops moving at 21 ins vacuum and not the correct 18" so that seems to add to the low voltage issues as well. I had the actuator loosened off (but not the adjustment nuts) a couple of years ago to see if the VNT arm was moving freely ( and it seemed to be) but I think now its time to dig deeper and solve this once and for all - even if the turbo needs to be cleaned out.
With only a genuine 20k on the clock (even though car is 12 years old now) I assumed the turbo could not be coked up but maybe I have to question that assumption now!
thanks again
John

Finally some progress!
I have managed to remove the actuator and find it is fully working : Gives 4.0 volts at 0 vacuum and gives down to 0.4 volts at 20 ins vacuum with a full range of movement.
The turbo lever is very stiff suggesteting a coked up turbo despite the low mileage! Looks like I need to remove the turbo and strip it down to clean out the coke. Not an easy task to remove it so going to investigate stripping it down in situ by seeing if anyone has done this. It looks doable but who knows. Will report back

Roy - A very belated update!
I did indeed manage to dismantle the turbo in situ (this saves a lot of work!) and it was heavily coked up despite the very low mileage.
I can only put this down to very few long drives and lots of cold starts to simply move the car a few feet each time in and out of my garage!
I was able to almost fully "decoke" the turbo but could not see how to remove the wheel housing the vanes (no screws or obvious holding mechanism) so had to rely on soaking this area with foaming Mr Muscle oven cleaner several times and, after an hour or two, rinsing the black sludge away until finally no more emerged.
The difference in the car became immediately noticeable with performance far more responsive and improved pulling and torque (even my wife noticed!). I have since done several 350 mile trips with only a very occasional limp mode remaining.
I think I shall remove the turbo again if I can figure out how to remove the vane wheel (the model is identical to the one in the video you sent me but viewing that does not show how the vanes are attached either) and try for a full mechanical coke removal. I cant anywhere find a video, description or exploded diagram of that particular vane setup however. Any suggested way to find out or do you know how that wheel is held in?
Any thoughts gratefully received.
Regards
John