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ECU not Communicating with vagcom....HELP!!!!

Discussion in 'A3/S3 Forum (8L Chassis)' started by camscockle20vT, Nov 30, 2010.

  1. camscockle20vT
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    camscockle20vT The stigs ugly brother

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    [Nov 30, 2010]
    hi all
    so heres the story.... my audi a3 1.8t sport will not start. i origanally checked battery... that was fine,then checked if the engine was getting fuel...that seems fine, then thought it myt be the immobiliser as i have a toad alarm system... but thats fine i think. so i got a freind to check it on diagnostic tool and it said cam sensor, so i got my mechanic to put his snap-on vagcom in to check in more detail, and it was having none of it,it wont communicate with the engine managment... it communicates with the airbag system but not the engine managment.he said it may be his computer thats not working seems doubtful as its communicating with other systems tho. he has told me to call AA as there computer may work but i havent got home start lol
    Any help would be much appreciated as im stuck with a car i cant start or find the problem.:sos:
    Last edited: Nov 30, 2010
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  3. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Nov 30, 2010]
    is the main engine control relay working? if not, no power to ecu no talkie
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  4. camscockle20vT
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    camscockle20vT The stigs ugly brother

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    [Nov 30, 2010]
    Ok mate thanks for the reply.
    how would i know if the relay is working?
    #3
  5. camscockle20vT
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    camscockle20vT The stigs ugly brother

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  6. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Nov 30, 2010]
    check power @ ecu is what I do with multimeter

    my wifes arosa did this.. dead engine control relay..
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  7. IGI
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    IGI Member

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    [Nov 30, 2010]
    also check ecu fuse first then as above ^
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  8. aragorn
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    aragorn "Stick a V8 in it!" Staff Member Moderator VCDS Map User

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    [Nov 30, 2010]
    The ECU doesnt connect directly to the Diagnostic interface, its looped through the cluster, and the cluster "forwards" the data on.

    First off check you can chat to the cluster, if you can, then you can pull the cluster out and join two pins in the harness to connect the ECU directly to the diag port and try again.

    If it works with the pins shorted, then its probably a cluster fault. If it doesnt work with the pins shorted, its an ECU fault.

    If you want to give it a go, i can find out which pins you need, if you tell me what year your car is and the exact model details.
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  9. badger5
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    badger5 www.badger5.co.uk Site Sponsor

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    [Dec 1, 2010]
    given its turned into a non starter, that sounds very reminisent of my wifes arosa and its faulty engine control relay
    no power, no communication
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  10. camscockle20vT
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    camscockle20vT The stigs ugly brother

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    [Dec 3, 2010]
    Hi all thanks for the help.
    The problem was with my mechanics vagcom as AA comp
    Worked fine. Its the crank sensor that had an open circuit
    so thats why it would not start. Explains why it would cut
    out now and again. 02 sensor is also nakered but i knew that
    already.
    Thanks again.
    #9

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