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Having an issue with voltage (bump stop mod)

This is a discussion on Having an issue with voltage (bump stop mod) within the External Engine forums, part of the LSx Technical Help Section category; I am attempting to do the bump stop mod to my throttle body but I am running into an issue. ...

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    2004 HEAD/CAM CTS-V 9t8z28's Avatar
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    Having an issue with voltage (bump stop mod)

    I am attempting to do the bump stop mod to my throttle body but I am running into an issue.

    I have piggybacked my DMM (volt meter) into the TPS sensor and at closed throttle (idle) I get around 9 volts. At WOT, I am getting around 4.7 volts.

    Now from all of the different threads on how to do this, only one of them tells you how to do it using a voltmeter. The rest instruct you to use tuning equipment which I do not have and use measurments in degrees of throttle.

    Here is the thread on using volts
    http://ls1tech.com/forums/showthread...hlight=writeup

    Using a voltmeter, I am supposed to see around .85 volts at idle and no more than 4.7 at WOT.

    I have plugged the (voltmeter) positive wire into the blue wire on the TPS and the ground obviously goes to a good ground. I have tried different settings on the voltmeter but to no avail. I have even moved to the two other wires on the TPS. One is hot and the other must be a ground.

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    2004 HEAD/CAM CTS-V 9t8z28's Avatar
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    come on peeps? Anything?

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    2004 HEAD/CAM CTS-V 9t8z28's Avatar
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    come on, somebody has to have done this mod!

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    The Bandit Wesman's Avatar
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    You should have 3 wires - reference voltage, signal, and ground. Reference voltage should be approximately 12 volts, and the signal wire should be your TPS voltage that the ECU is seeing.

    So if you've got your DMM in the 12VDC position and you've got the black on a good ground (negative battery terminal works well) and the red probing the signal wire, you should get your signal voltage. The readings you are getting are very strange for sure.

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    2004 HEAD/CAM CTS-V 9t8z28's Avatar
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    Quote Originally Posted by Wesman View Post
    You should have 3 wires - reference voltage, signal, and ground. Reference voltage should be approximately 12 volts, and the signal wire should be your TPS voltage that the ECU is seeing.

    So if you've got your DMM in the 12VDC position and you've got the black on a good ground (negative battery terminal works well) and the red probing the signal wire, you should get your signal voltage. The readings you are getting are very strange for sure.
    Thanks for the help. I just can't figure it out. I guess that I will try the battery ground as apposed to the ground coming from the underhood fuse box.

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    Senior Member camarojunky74's Avatar
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    okay, i think i understand what your trying. here goes.

    wesman, reference voltage is 5 volts not 12.

    other than that your explanation is spot on, good luck brandon

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    The Bandit Wesman's Avatar
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    Quote Originally Posted by camarojunky74 View Post
    okay, i think i understand what your trying. here goes.

    wesman, reference voltage is 5 volts not 12.

    other than that your explanation is spot on, good luck brandon
    Good call, thats my bad. For some reason I had 12 in my head...

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    2004 HEAD/CAM CTS-V 9t8z28's Avatar
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    Still no luck. Same readings using a different ground.

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    Maybe its cause its a 98? Wasn't something different with the 98/99 throttle bodies?

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    Senior Member camarojunky74's Avatar
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    Quote Originally Posted by squee View Post
    Maybe its cause its a 98? Wasn't something different with the 98/99 throttle bodies?
    yeah, but the tps sensor and wiring is the same.

    brandon when i get home from work, ill uncover the car, and see what i can get when doing mine.

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    2004 HEAD/CAM CTS-V 9t8z28's Avatar
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    Quote Originally Posted by camarojunky74 View Post
    yeah, but the tps sensor and wiring is the same.

    brandon when i get home from work, ill uncover the car, and see what i can get when doing mine.
    Cool! Thanks

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    2004 HEAD/CAM CTS-V 9t8z28's Avatar
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    Quote Originally Posted by squee View Post
    Maybe its cause its a 98? Wasn't something different with the 98/99 throttle bodies?
    The engine and brain is a 99

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