vw sharan tdi low power ahu engine

Discussion in 'VW Mk3 Jetta, Passat TDI and other/older diesels' started by landroverbob, Dec 31, 2010.

  1. landroverbob

    landroverbob New Member

    Joined:
    Dec 30, 2010
    Messages:
    10
    Car:
    sharan 1998 passat3, golf2, land rovers, argocat
    Should this be a fresh post as it may detract from the OE post.?
    The car is a Sharan TDI belonging to a financially challenged friend -Its left hand drive and in france
    Engine AHU, first reg 17th august 1998. Car vin number is: wvwzzz7mzxv013***. Would this be an NVT turbo?, on the turbo plate is 11989/600-30K J1075/1820. -Could be the odd incorrect number due to reading in a mirror lying on the garage floor upside down with head and arm jammed round the driveshaft. .

    I now have the car with me today and have spent this morning on it. Road testing last week from cold it dropped power for the first time part way up a hill after a 20k drive (thrash). I came back ,had a quick look, replaced a section of worn vac hose (under bonnet - to MAP sensor in ECU) Road tested again and power dropped off again at exactly the same place as before (sneaked another scan,clear and res-can with original fault code reappearing), back to base,another look round, disconnected and reconnected turbo valve and all the other sensors I could easily reach. Road tested again and exactly same result. Working on it again today I road tested it and exactly the same as before but found if I switch off then back on (read to try this on forum) then it is ok until next high boost demand then power goes down again. When it does this it is instant and very obvious, feels just like a turbo hose has blown off

    I then replaced more vac hoses as ness, had the codes read, cleared and read again comes up with 65535 035.on one scanner and "permanent ecm fault" on another - neither proper VW scanners. Asked for turbo boost readouts but circumstances (garage boss came back) and the only one we had time to record was "desired boost 795, -"boost pressure 979". Seems a fair difference does that confirm it's overboosting? Got back to base and then checked the turbo operating valve which gave the correct figures according to Autodata
    Another problem I encountered was the engine cut out as I braked to 10kph to turn down a side road after driving about 30k (the last 2k up a long uphill gradient at only 65/75kph due to the power loss). Wouldn't fire at all on the first attempt to start, fired intermittently after a while on the second attempt, better on the third attempt then eventually picked up properly and revved ok. Sneaked probably the last free scan ever, no other fault than the previous one still recorded.THe owner says it has done that before and is doing so more frequently.Last thing I did was replace the fuel filter I had ordered days ago (this is france). I did notice the fuel pipe in at the filter was perished / split so I shortened it slightly and do wonder if it was drawing air in before and causing a problem. Sneaked the very very last free "clear and reread" scan - no change, same fault recorded

    Logic tells me ECU wants replacing but they are expensive and look a b*ga to get out and I have read that others have done that and been wrong

    Just read the new post and will check actuator tomorrow but could do with knowing how to ID the turbo type if the number above can't and also does the ecu control limp mode by reducing turbo boost or fuelling ????.
    Got involved with this to help out and I obviously know all about VW's as amongst my fleet I have a golf mk2 diesel na and a passat '93 tdi (GO SLOW BUT GET THERE CARS)!!!
    login to remove this ad
  2. chittychittybangbang

    chittychittybangbang Administrator

    Joined:
    May 23, 2007
    Messages:
    22,071
    Car:
    2006 Jetta TDI
    Location:
    CT
    post moved to mk3 forum because of the engine. We didn't have that engine here so not 100% sure but I checked the parts catalog and I'm pretty sure it's not a VNT turbo.

    The ecu fault is the hose inside the ECU. EVERY mk3 TDI will have it. http://www.myturbodiesel.com/1000q/a3b4/ecu-hose-chip-tdi-65535.htm See this writeup for details, classic error code, fix it first and see if it makes the difference. The vac line goes to the sensor.
  3. landroverbob

    landroverbob New Member

    Joined:
    Dec 30, 2010
    Messages:
    10
    Car:
    sharan 1998 passat3, golf2, land rovers, argocat
    thanks chitty

    After posting last night googled the turbo numbers I had and when I reversed them (duh-me) found they referred to the non NVT turbo so can discount the sticky vane problems and so assume it's got to be 1 -the hose in ecu, 2-the ecu/ mapsensor, 3-the n75 boost valve, 4- the wastegate adjustment or 5 -wastegate diaphragm and re -"If you are getting a check engine light (CEL or MIL) and see "65535 - Internal Control Module Memory Error" with a VCDS tool, it's most likely caused by this leaky hose"--No check light coming on this car. Also I looked at the link given in your reply thanks and that is right for this car



    1 - Re --"There is a hose inside the ECU that will wear out. This hose connects to an air sensor inside the ecu. If an air leak occurs in this hose, the car will not run correctly". - I checked before and the hose holds vacuum but it's a pressure sensor on this model of turbo so unles told not to I'm going to see if I can test it tomorrow using around 1000mb/ 14psi pressure from the airline and a leakdown setup I have.
    2 - can't test this myself
    3 -N75 valve - have checked it's resistance and thats correct
    4 -wastegate adjustment -got no info on that
    5 - wastegate diaphragm, put around 1000mb / 14psi to it this morning and it operates ok

    If the map sensor pipe was leaking how does our ecu know the boost pressures are wrong as the boost readings (as in previous post "desired boost 795," -"boost pressure 979") let me think the sensor is working to be able to make this comparison. They were not taken when under load but stationary in the car and I'd have thought these would be much higher when under load. Ive Tee'd in a boost guage and am going to road test again tomorrow and see what boost presure under load is achieved.
    As regards the cutting out when I braked -any idea if it could be to do with the brake pedal switch
    Any more thoughts are most gratefully received!!

    Moderator, when this was moved to the Mk3 section it didn't email me with an update to say it was moved, not a winge just thinking of others in the future.
  4. landroverbob

    landroverbob New Member

    Joined:
    Dec 30, 2010
    Messages:
    10
    Car:
    sharan 1998 passat3, golf2, land rovers, argocat
    more of same

    Just been on road test, different route to previous runs but approx same distance, stopped for half hour at pals house, went to fetch some bread from shop -15 minutes- then back onto the hill that it always looses power on which it did in exactly the same place! I had a boost guage on which was peaking at 10psi when the power drop occured (reached that pressure many times before during this run without drop of power)but after the drop it would still run around 4/5psi and boost to 10psi even though the performance was just as if there was no boost. Switch off and then on again and power back on till under heavy load again (10psi of boost). Knock it out of gear and it would rev up to 5000 freely even though the power was still in "poor mode" Am I right in thinking this isn't "limp mode"
    So obviously it is resetting something -anyone any ideas? I suppose I could believe the fault code that says permanent ecu fault and admit defeat replace it but my time is free and an ecu is very expensive for a one parent friend to buy. Going to play with maf sensor now.
  5. audi1z

    audi1z Member

    Joined:
    Oct 16, 2010
    Messages:
    256
    Car:
    Audi 80 1Z Engine
    Hi,
    The error 65535 may but must not mean a faulty ECU. It may also be a communication problem.
    Which diagnostic tool do you use, original VCDS? Which version and which interface? Potentially you must check the communication settings.
    From your descrption one can only guess that the charge pressure control of the AHU Wastegate Turbocharger works incorrect, but one needs a correct communication with he ECU, a readout of the error codes (behind ECU "failure"), and a readout/log of measurement blocks during driving, mainly #11.
    Do not "test around" with too many items, it will not help.
    (BTW, I drive a 1Z Engine, which is identical to the AHU, with more than 350 Tkm).
    Brgds,
    Audi1Z
  6. landroverbob

    landroverbob New Member

    Joined:
    Dec 30, 2010
    Messages:
    10
    Car:
    sharan 1998 passat3, golf2, land rovers, argocat
    AUDI1Z Thanks for input, scanner was auto-diag which I don't have access to very often so can't obtain the information you mention. The first time but not since the code recorded was 65 535 035. As regards the message and fault code not been taken too literally as a permanent ecu fault and possibly being communication problems or one that is not recordable thats really what I'm trying to establish.
    I figured as the boost pressures don't vary whether performance is proper or after it drops in power showed the problem doesn't lie in the valve or sensor or pipework
  7. audi1z

    audi1z Member

    Joined:
    Oct 16, 2010
    Messages:
    256
    Car:
    Audi 80 1Z Engine
    Hi,
    My input was only an advice. It´s your car. I only see that you do not have available the data from the workshop manual, nor a proper VCDS version for failure search. And, I do not want to be unpolite, but your writings indicate that your understanding of the engine control is not complete.
    Brgds,
    Audi1Z
  8. landroverbob

    landroverbob New Member

    Joined:
    Dec 30, 2010
    Messages:
    10
    Car:
    sharan 1998 passat3, golf2, land rovers, argocat
    Compliments on your english but be as impolite as you wish if it helps me to mend this car and I'm sure my knowledge isn't complete or I wouldn't be asking questions but what part have I got wrong so far? I am quite happy to told where I'm going wrong.
  9. audi1z

    audi1z Member

    Joined:
    Oct 16, 2010
    Messages:
    256
    Car:
    Audi 80 1Z Engine
    Hi,
    Please take my apologies if my words were too hard. If you still like, let´s go back to the problem.
    What you observe is symptomatically for an engine going into limb mode because of a temporary error observed by the ECU, lasting for some seconds and classified dangerous for the engine.
    Once you stop and re-ignite, or even let go the gas pedal and then throttle up again, the limb mode is left, and the engine comes up again.
    Typical fault conditions are a too high manifold pressure (overshoot), or a misrelation between manifold pressure and intake air mass. The latter would happen if e.g. the ECU internal hose to the pressure sensor would have a leak, but other reasons are credible, too. I personally had this situation with defective intake hoses, but also with oil in the hose going from the intercooler to the pressure sensor in the ECU. When you reach a certain load condition, engine power is suddenly gone.
    For the case you can not find a broken intake hose, or another evident mechanical defect, the search becomes more difficult.
    Without having measurement equipment, you can perform a driving test with the N75 regulator valve electrically disconnected. When the fault disappears, either the valve or its supply is defective (I have read that you measured the valve resistance), nevertheless do the test.
    For further checks, you need to read out the ECU during defined driving conditions, particularly the requested/real values for the intake manifold pressure, and the control level of the N75 pressure boost valve.
    Manufacturers values for turbocharger check are:
    Full throttle acceleration from 1500min-1 to 3000min-1. Manifold pressure to be reached at 3000min-1 is 1550 mbar to 1750 mbar w/o N75 operating, 1800mbar to 2050 mbar w/ N75 operating.
    Note that this test must not detect all faults when done with an external pressure gauge, it is important what the ECU reads.
    Error 65535 is imho no indication for a failure in the intake pressure tubing. The ECU can not distinguish between a leak inside, and a leak outside, in the sensor tube or in the intake hoses. All is connected together.
    Brgds,
    Audi1Z
  10. chittychittybangbang

    chittychittybangbang Administrator

    Joined:
    May 23, 2007
    Messages:
    22,071
    Car:
    2006 Jetta TDI
    Location:
    CT
    Correct.

    landroverbob, have you removed the tubing inside the ecu and visually inspected it? Perhaps testing under vacuum the hose cracks pulls tight but under pressure the crack is exposed? You say you vacuum tested it but I have to ask if you visually inspected it since it's such a common problem.
  11. landroverbob

    landroverbob New Member

    Joined:
    Dec 30, 2010
    Messages:
    10
    Car:
    sharan 1998 passat3, golf2, land rovers, argocat
    AUDI1Z

    --*Apologies entirely unnecessary, help is appreciated. Just to explain some circumstances , I am non french technical speaking living in rural france, the garage is 20k from my farm and are helpful but always very busy, the car belongs to a one parent family with little budget to spend and garages are known to take advantage or just keep fitting parts until it's mended. - All my own vehicles/toys are deliberately non electronic*
    What you observe is symptomatically for an engine going into limb mode because of a temporary error observed by the ECU, lasting for some seconds and classified dangerous for the engine. *I understand that but - when at the garage last week we cleared the ecu memory the fault reappeared immediately the engine was run again, before driving it on the road. I then drove it on the road for a few k's till going up it's favourite hill the power dropped as per usual*
    Once you stop and re-ignite, or even let go the gas pedal and then throttle up again, the limb mode is left, and the engine comes up again.--*Only switching off then back on resets it from limp, throttle change doesn't*
    Typical fault conditions are a too high manifold pressure (overshoot),--*maximum was around 1bar /15psi on my temporary tee'd in boost gauge*
    or a misrelation between manifold pressure and intake air mass.-- * I intend doing the air mass next on the garage auto- diag and will try to get them to let me do manifold pressures too*
    The latter would happen if e.g. the ECU internal hose to the pressure sensor would have a leak, *I tried vacuum testing initially and since then a pressure test and it holds 18psi without dropping, when I replaced part of the worn hose that goes to the ecu I also cut it open and found it free of oil inside*
    but other reasons are credible, too. I personally had this situation with defective intake hoses, but also with oil in the hose going from the intercooler to the pressure sensor in the ECU. When you reach a certain load condition, engine power is suddenly gone.
    For the case you can not find a broken intake hose, or another evident mechanical defect, the search becomes more difficult.
    Without having measurement equipment, you can perform a driving test with the N75 regulator valve electrically disconnected. --* I have not done that as I had the boost gauge fitted and it still produced the same boost after the power dropped -but I will do that tomorrow anyway*
    When the fault disappears, either the valve or its supply is defective (I have read that you measured the valve resistance), nevertheless do the test.
    For further checks, you need to read out the ECU during defined driving conditions, particularly the requested/real values for the intake manifold pressure, * thats one thing I will have difficulty doiung but will be trying*and the control level of the N75 pressure boost valve.
    Manufacturers values for turbocharger check are:
    Full throttle acceleration from 1500min-1 to 3000min-1. Manifold pressure to be reached at 3000min-1 is 1550 mbar to 1750 mbar w/o N75 operating, 1800mbar to 2050 mbar w/ N75 operating. --* it never exceeds 1bar/15psi under full throttle load which is the pressure I have used to mechanically test the actuator fully opens the wastegate - are you sure of those figures, isn't 2050mb around 30psi?*
    Note that this test must not detect all faults when done with an external pressure gauge, it is important what the ECU reads.
    Error 65535 is imho no indication for a failure in the intake pressure tubing. The ECU can not distinguish between a leak inside, and a leak outside, in the sensor tube or in the intake hoses. All is connected together.

    Hope you can understand my replies LRB.
  12. landroverbob

    landroverbob New Member

    Joined:
    Dec 30, 2010
    Messages:
    10
    Car:
    sharan 1998 passat3, golf2, land rovers, argocat
    Thanks Chitty, ecu is behind the dash and a real pig to get to so I have had pressure tested it through it's own hose fom the manifold end and it maintains 18 psi. Also when replacing part of ther original hose I cut open the piece I removed and found it dry of oil inside. The inlet pipe from the intercooler to the manifold which the map sensor hose is fitted into is rather oily inside however. Answered Audi1z with a long reply, asked him if his boost test figures were correct, sounds a lot of boost or am I misunderstanding?
  13. audi1z

    audi1z Member

    Joined:
    Oct 16, 2010
    Messages:
    256
    Car:
    Audi 80 1Z Engine
    Hi,
    The communicated test pressure figures are absolute pressure (manufacturer original), not pressure relative to 1 bar/ambient.
    Because the error message you refer to seems to originate from a potentially bad communication with a third party measurement device, you should consider to visit a Volkswagen Service and to ask there for readout of the ECU error codes. The alternative would be to purchase (or at least loan) an original VCDS from Ross-Tech, with correct set-up of the interface.
    Regards
  14. landroverbob

    landroverbob New Member

    Joined:
    Dec 30, 2010
    Messages:
    10
    Car:
    sharan 1998 passat3, golf2, land rovers, argocat
    sharan

    Once again thanks Audi1z and Chitty
    Disconnected the n75 and road tested and the power drop/limp occured on cue. I took the bosch maf sensor out to get the numbers in case I needed them and as expected it looked ok.
    I was able to use the scanner at the garage late afternoon and drove the car with it plugged in, the actual boost pressures agreed approximately with the desired pressures and were within the parameters you gave (I understand why they seemed high to me now you have explained) but unfortunately the scanner battery failed before I reached the hill where problems occur and before I could try the maf comparisons and when I returned to the garage it was closing time so I could not carry on.
    I am hoping to rely on their good nature to let me try again and I'll post the results
    I can't remember if I have said but disconnecting the maf sensor when the car is running correctly produces the same power drop and driving feel but I guess it has gone into limp mode then so bound to be the same.

    I quite accept that the scanner may be correct and there is an ecu problem and will need to be replaced but have read several posts where that's been done on the basis of fault codes and not fixed the problem. It's not my money I'm spending so I want to be as sure possible before doing
    that and of course for me is understanding how it all works plus making information available to others with problem cars.
  15. landroverbob

    landroverbob New Member

    Joined:
    Dec 30, 2010
    Messages:
    10
    Car:
    sharan 1998 passat3, golf2, land rovers, argocat
    is it the ecu or maf

    Was able to use scanner yesterday, cleared all faults. Couldn't have the scanner again for an hour so the car was parked up. I then drove it with the scanner connected and set to view "desired air flow" and "actual air flow." Comparison pretty close under all throttle conditions, slight lag under fierce aceleration but after about 20kms gradually getting a bigger difference between readings on sharp pedal depression. On the problem hill in the by now usual place in 4th gear, full throttle around 4000rpm it went into limp mode. Traffic caused me stop and when stationary at tickover both readings were the same, revving the engine to 4000rpm the "desired" read 830 when the "actual" read 590. I repeated this several times with similar results then went into fault reading and for the first time ever got intermittent air mass metering fault as well as the usual permanent ecu fault. Would anyone think it can be the ecu. It's a bosch meter 0280 217 121 copies are cheap on ebay and feedback shows they work even if perhaps not for long? but I will ask around first and see if I can borrow a working unit to tryfirst
  16. chittychittybangbang

    chittychittybangbang Administrator

    Joined:
    May 23, 2007
    Messages:
    22,071
    Car:
    2006 Jetta TDI
    Location:
    CT
    There's always a possibility of a problem with the ECU, maybe the sensor inside the ECU is bad instead of the vacuum line. but that error code is normally a bad vacuum line somewhere along the sensor's route. The meter going to only 590 actual when 830 is requested indicates a problem. However, since it's new, try fixing the first problem first. The meter not going to max could be clogged exhaust, bad EGR, bad EGR control (the EGR displaces the intake air), and of course, bad air flow meter.
  17. Seatman

    Seatman Active Member

    Joined:
    Jul 9, 2010
    Messages:
    5,222
    Car:
    2000 Mk4 Golf Estate 1.9tdi 174 bhp
    Location:
    Scotland
    Mods:
    PP764's, turbo and mapping
    Don't forget the waste gate can stick, that's what happened on my Cordoba. I would just make sure the actuator rod moves freely just in case. As for the ecu on your sharan being awkward, I think most things on them are a touch awkward. My friend has one and doing the timing belt and brakes was a bit of a challenge especially getting brake fluid into the resivior. Also what about the possibility of the actuator having a damaged diaphram? I would check it despite what the boost gauge reads just to be certain.:)
  18. audi1z

    audi1z Member

    Joined:
    Oct 16, 2010
    Messages:
    256
    Car:
    Audi 80 1Z Engine
    Hi,
    0280 217 121 is not the complete part number. There is surely a letter belonging to the P/N, and this is important.
    Regarding the error code 65535, again, the ECU can not distinguish between a leak in the sensor hose and the intake. It a leakage case, it will display something like 00575-xxx, but not 65535. 65535 is originally a defect ECU (computer), but also indicates a communication problem.
    The observation indicates that the engine gets under high load too less air. One cause may be a defect in the exhaust gas recirculation. Does it close?
    Regards
  19. ixeras

    ixeras New Member

    Joined:
    Aug 14, 2011
    Messages:
    1
    Car:
    VW Sharan 1,9tdi 2001
    Hey!
    I have the same problem with my sharan AUY.
    Came error codes: air mass meter incorrect- I have changed
    turbo regulating problem
    I found diaphragm in EGR was broken- EGR valve was changed.
    Now the car does not miss the power, but it sneezes with releasing gas pedal after high rpms just like before.
    Sorry about my english.
    Edvard
  20. JoesAuto

    JoesAuto New Member

    Joined:
    Sep 13, 2011
    Messages:
    1
    Car:
    76 Super Trans-Am
    Mods:
    400 cu in, 2.11 intake valves, 750 Holley, Blue bo
    Just a thought....

    .... I live in the mountains in Eastern Oregon, not exactly sure if your model is similar. We have several TDIs running around here, on several occassions we have had the intake completely plug up with carbon. I have seen these occompanied with intake codes. They are easy to inspect and fairly easy to clean out. Definately a lack of power and for whatever reason better and worse at times, but even with full boost it just cant get past the carbon. Again not sure if it is applicable here but the complaint sure sounded familiar!!!
    Good luck!!!

Share This Page