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  1. #1
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    Member No: 94149 AlexE38 is an unknown quantity at this point AlexE38's Avatar
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    ABS/ASC+T lights constantly on and Choke Valve

    I have the ABS/ASC+T lights constantly on and the BMW (not OBD) fault code is 40 (Potentiometer, choke valve). I also have a feeling that the throttle response is not as quick as it used to be (RPMs don't increase as quickly when the car is parked and I press the gas pedal).
    I found in TIS that ABS/ASC unit needs to be reinitialized whenever the potentiometer is replaced/removed (I removed it).
    I couldn't find the explanation for this reinitialization procedure (even on this board) but found on google information abaout calibrating the potentiometer (not BMW but stil ASC related). Basicaly the throttle choke valve is open copletely and then the software is instructed to tell ASC unit to memorize the opening angle (as provided by a potentiometer). Then the throttle choke valve is fully closed and again the opening angle is memorized by ASC unit. This supposedly "teaches" the ASC unit how to correctly read the potentiometer in order for fuel injection system to create the right mixture. If
    My guess is that this procedure is refered as ASC unit reinitialization in TIS.
    Does anyone have any idea if I'm going in the right direction or any information on BMW ASC code 40? I don't wan't to go to a Stealer just to make him laugh.


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    Re: ABS/ASC+T lights constantly on and Choke Valve

    fc 40 can mean that the choke valve is not operating at all,as the
    potentiometer is the control unit's only source of feedback for the
    movement of the valve.that valve, if you look closely,has a cable
    driven by an electric actuator mounted in lf fender.approx every
    other time you cycle the key 'on' that electric actuator operates
    the cable to close that valve for a pre-drive check.all the potentiometer is telling the control unit is a voltage value that
    corresponds to the position of the valve.if the valve doesn't move
    fc40.if the voltage value does not change in a linear fashion,fc40.
    this is a safety item-now go to your 'stealer' to let them properly
    diagnose and repair it.

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    Re: ABS/ASC+T lights constantly on and Choke Valve

    Thanks for your info, it cleared some things for me.

    I checked the actuator and it works as you said, it closes the valve approx. every other time you turn the ignition key. The potentiometer also changes resistance in a linear fashion when the valve is closed or released (open). I checked the potentiomer resistance at the conector in the fuse/relay box which means that the cables are good as well.

    The only thing left is the ABS/ASC control unit. It either needs to be reinitialized (if such procedure exists) or it is bad.

    Alex

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    ABS/ASC+T control unit = $$$$


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