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Thread: Audi A4 Won't Start, Brake Lights On

  1. #1
    Join Date
    Aug 2010

    Post Audi A4 Won't Start, Brake Lights On

    I wonder if someone can help.
    I have a 2003 Audi A4 1.9 TDi which has an irregular fault.
    Sometimes when turning on the ignition the ABS warning light stays on and the brake lights illuminate without the brake peddle being pressed. The car will not start, although the engine does turn over.
    This can only be reset by leaving the ignition on for a period of time, typically 3 - 5 minutes until the waring lights go out as do the brake lights. The car can then be started normally.
    This fault has no regular pattern, it has displayed this simptom for the past 2 days, the last time it did so prior to this was around 2 years ago. Once the fault has reset the car will start normally many times, today for example it started normally in the morning and then would not start in the car park after shoppong for a couple of hours. It has been ok since and has been started 3 times for separate journeys.
    Any feedback would be greatly appreciated.

  2. #2
    Join Date
    Apr 2009


    Until someone, posts who knows the car:
    If it was my car, I would assume the ABS system is trying to tell me something. I would, get to a dealer and ask or at least find a longish straight clear road and brake very hard, try to make it skid, forcing the ABS to work, you should feel it working - a sort of pulsing or vibration through the brake pedal - if the ABS is healthy or the car will skidd if it is not.

  3. #3
    Join Date
    May 2007


    There is a chance it could be the battery is going or a bad connection.

  4. #4
    Join Date
    May 2008


    If the ABS light is staying on for a time, a fault code may well be stored in the ABS computer. A scanner may help on a diagnostic check.
    In the meantime, I think I would replace the brake switch above the brake pedal. In the VW group these are known to be very poor and cost just a few pounds. There is a technique to the correct fitting of them which is on most Audi/VW forums.

  5. #5
    Join Date
    Aug 2010

    Default Found problem

    Hi all,
    found via a little trial and error the fault was caused by relay 373 being loose. Pressed home and fault has cleared. Relay 373 is the headlight and brakelight test relay.

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