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Thread: Case study: 01986 - Convertible Top Frame Position Sensor (G356)

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    VCDS Distributor NEtech's Avatar
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    Case study: 01986 - Convertible Top Frame Position Sensor (G356)

    Audi A4 Cabrio 2008
    Periodic Convertible Top could not close.



    G365 changed.

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    Verified VCDS User DV52's Avatar
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    NETech: very interesting - I probably should know the answer, but what are the scales in the graph? Sorry, but graphs without axis descriptors is a pet-peeve of mine!!

    Don
    VW Golf MkVII (MY13) - A3 8V hatch (MY17)

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    Benevolent Dictator Uwe's Avatar
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    Quote Originally Posted by DV52 View Post
    NETech: very interesting - I probably should know the answer, but what are the scales in the graph? Sorry, but graphs without axis descriptors is a pet-peeve of mine!!
    I believe MVB 001.4 in that 0x26 module is a field that lacks units; it's just a value with a range of 0 to 255.

    -Uwe-
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    VCDS Distributor NEtech's Avatar
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    Yes potentiometer (G365) raw values.

    1 kOhm

    Last edited by NEtech; 07-13-2020 at 12:41 AM. Reason: picture

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    Ross-Tech Employee Jef's Avatar
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    Thank you, indexed.
    Jef
    Ross Tech Support Team, Alpha Squad
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    Benevolent Dictator Uwe's Avatar
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    Quote Originally Posted by NEtech View Post
    Yes potentiometer (G365) raw values.
    Those kinds of position sensors are designed in such a way that the raw value never goes to the extreme end of the range (in this case, 0 or 255), and if it does, the control module interprets that as a malfunction.

    -Uwe-
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    Verified VCDS User DV52's Avatar
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    ^^^^^^^hmm...... OK, so notwithstanding that NETech's picture shows a variable 1Kohm resistor, the chart (module?) quantizes the readings from pot's slider into 255 x positions along the roof's travel. I assume this is what Jeff means by "indexed". Makes sense - but what then causes the lag in the new sensor's trace? Isn't the horizontal scale time and if so, just changing the sensor shouldn't alter the time response of the roof from the starting position?

    Don
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    VCDS Distributor NEtech's Avatar
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    This is just 2 different open/close runs, one good and one bad.
    I have defined the x-scale start and stop, I made a offset so it is easier to see.

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    Ross-Tech Employee Jef's Avatar
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    Indexed, as in I added this thread to the super sticky index.
    https://forums.ross-tech.com/showthread.php?18464
    Jef
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    Quote Originally Posted by Uwe View Post
    Those kinds of position sensors are designed in such a way that the raw value never goes to the extreme end of the range (in this case, 0 or 255), and if it does, the control module interprets that as a malfunction.

    -Uwe-
    Interesting. I suppose the potentiometer is connected to a VCC and the voltage on the cursor is read by an analogue-to-digital converter (one byte, values 0 to 255) with limits defined by the controller module. But if there is some dust on the potentiometer's resistive track it can make the cursor to lose contact with the track, then the voltage on the cursor can go momentarily to zero, even though it's a value out of range. Am I correct?

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