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No epc light , non start

Discussion in 'A3/S3 Forum (8L Chassis)' started by cctuning, Mar 11, 2014.

  1. cctuning

    cctuning New Member

    Dec 18, 2008
    Likes Received:
    Hi, I've got an Audi S3 8l 2002 and intermitantly the epc light is not there and I get no communication to the ecu,also the fuel pump does not prime when this happens. There's no dtc's as the ecu losses it's com's.
    ive changed the main ecu relay and fuel pump relay but still the same.

    Im thinking maybe ECU but not 100% sure as when I go to test it then starts to work again so alls ok.

    Thanks in advance
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  3. @udi A3

    @udi A3 Site Sponsor
    Site Sponsor VCDS Map User

    May 25, 2012
    Likes Received:
    How are you testing the ecu? In this situation to test ecu i would program a new one in and leave it there till the fault repeats. However if there is a short somewhere causing this you risk damaging the second ecu.
    Use measuring block 125 in various modules with vcds to try to establish the comms lost.
    I have no real experience with petrol so cant point out any common failure points on your engine.
  4. s3dave

    s3dave TFSI Hybrid

    Nov 11, 2009
    Likes Received:
    I would check earths under the battery, then make sure the ECU is not sitting in water (under the scuttle panel)

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