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Thread: ASC+T Mystery Solved

  1. #1
    Join Date
    Mar 2005
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    E34 540i 6sp 1995-03-28

    ASC+T Mystery Solved

    So since getting this 540/6 last July the ASC light would not go out when depressing the ASC button meaning the system was not ON.

    I finally before bringing it to a BMW trained shop for diagnostic decided to try swapping the two throttle position sensors. The plugs do have slight differences in the cover but they do each fit on the other sensor..

    This was in fact the problem.. Immediately the ASC light went out , the rough and surging idle I assumed was a sticking ICV all vanished and the engine performance noticeably improved though it wasn't really bad other than the idle issues... just much faster responsiveness to throttle.. Now I can drive carefree in Snow again and get on to other issues..

  2. #2
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    Thanks for that follow up. Don't you want to strangle the guy who did it?

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

  3. #3
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    Quote Originally Posted by ross1 View Post
    Thanks for that follow up. Don't you want to strangle the guy who did it?
    Or the engineer who failed to make the connectors unique?

  4. #4
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    E34 540i 6sp 1995-03-28
    Kind of annoyed with myself for not trying it right away. I considered it at one point but it seemed too easy and simple and I am rarely that lucky so kept looking for something else.
    Quote Originally Posted by ross1 View Post
    Thanks for that follow up. Don't you want to strangle the guy who did it?

  5. #5
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    It's an easy assumption that something is assembled correctly when we start a diagnosis. This is a good reminder that isn't always so.
    I have a sneaking suspicion the M20 no start thread currently a few threads down has a similar problem.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

  6. #6
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    Quote Originally Posted by ross1 View Post
    It's an easy assumption that something is assembled correctly when we start a diagnosis. This is a good reminder that isn't always so.
    I have a sneaking suspicion the M20 no start thread currently a few threads down has a similar problem.
    Agreed. Went through this rebuilding tundra v6. Learned the value of labeling connectors....

  7. #7
    Join Date
    Mar 2005
    Location
    Long Beach, CA
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    93BMW 525i/95 BMW 540i/6
    Actually my mechanic made the same mistake. I don't remember what repair the E34 was in for. I picked the car right before they closed and noticed the ASC light as well as the idle. I was going to bring it back the next morning, but got to tinkering around at home and switched the sensors. Voila!!! I agree: BMW should have designed the connectors to be different so this should never be an issue.
    USC Ralph - Long Beach, CA USA
    1989 E34 White 525i (M20) 310,000m (Sold)
    1993 E34 Black 525i (M50) 308,955m
    1995 E34 Calypso Red 540i/6 (M60) 201,254m
    1993 E34 Black 525iT (M50) 138,500m

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