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speedometer needle jumping???

This is a discussion on speedometer needle jumping??? within the General Help forums, part of the LSx Technical Help Section category; It works fine for a couple of mins after I start it up but once I drive after that the ...

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    Junior Member TruThug's Avatar
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    speedometer needle jumping???

    It works fine for a couple of mins after I start it up but once I drive after that the needle starts jumping up and down. It does not have a certain speed that it starts jumping just happens whenever. When I come to a complete stop it again jumps up and down just to reach 0. Why is this happening? Also Everything is stock.

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    Sounds like a wiring or connection issue.

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    Quote Originally Posted by TruThug View Post
    It works fine for a couple of mins after I start it up but once I drive after that the needle starts jumping up and down. It does not have a certain speed that it starts jumping just happens whenever. When I come to a complete stop it again jumps up and down just to reach 0. Why is this happening? Also Everything is stock.
    What wound up being the problem with your speedo needle jumping around? My 2000 TA has been having the same problem.

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    Member Ant71130's Avatar
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    Please correct me if I'm wrong, I haven't had this issue with a newer car but is the speed sensor connected to a gear in the tranny or diff? Sometimes when those gears get stripped it can cause fluctuation. However if it doesn't go back to 'correct' after it jumps and simply bounces then I'd say it's electrical for sure.

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    Quote Originally Posted by Ant71130 View Post
    Please correct me if I'm wrong, I haven't had this issue with a newer car but is the speed sensor connected to a gear in the tranny or diff? Sometimes when those gears get stripped it can cause fluctuation. However if it doesn't go back to 'correct' after it jumps and simply bounces then I'd say it's electrical for sure.
    Mine is definitely electrical. It only happens in warm weather. I already had the Vehicle Speed Sensor replaced. I just ordered a new ECM off ebay - hopefully that will fix it.

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    expensive tires az gt eater's Avatar
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    The only time I saw that happen on my car was a bad alt. And it went crazy continously. You may have a bad BCM. Body Control Module.

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    Quote Originally Posted by az gt eater View Post
    The only time I saw that happen on my car was a bad alt. And it went crazy continously. You may have a bad BCM. Body Control Module.
    Is the BCM physically located under the hood or in the passenger compartment?

    My speedo needle falls when I gradually push on the gas. If I push the gas down hard, it doesn't tend to do it. At lower speeds, it will cause the transmission to downshift. That's really annoying. It's been doing it for quite a while.

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    Member MudStainKILLA's Avatar
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    Quote Originally Posted by az gt eater View Post
    The only time I saw that happen on my car was a bad alt. And it went crazy continously. You may have a bad BCM. Body Control Module.
    +1 to the alt as a possibility, my bird was doing some odd stuff electrinics wise and it turned out to be a bad alt and low battery.

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    Quote Originally Posted by MudStainKILLA View Post
    +1 to the alt as a possibility, my bird was doing some odd stuff electrinics wise and it turned out to be a bad alt and low battery.
    The battery was replaced within the last year. You have to figure that I am an old guy, when I say it's been doing it "for a while" I mean it's had the problem for at least 5, maybe 6 years.

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    Member MudStainKILLA's Avatar
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    you wern't joking when you said a while! well i guess that rules out that as a possibility...
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    expensive tires az gt eater's Avatar
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    I don't have much more to add. I do know that your speedo doesn't have a cable running to the instrument cluster. The cluster just snaps into a wire connector. I would think that somewhere in the tranny there is an actual gear. Maybe that is your problem. Stripped out, or skipping. I reread your first post, and I would say that it most likely is your BCM. It is located up in front of pass foot well. I have no experience with it, but have seen many threads about it. Radio and power windows stop working at same time Here's one. http://www.ls1.com/forums/f6/electrical-problem-165491/ Here's another one with some helpful pics from Smittro.

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    Quote Originally Posted by az gt eater View Post
    I don't have much more to add. I do know that your speedo doesn't have a cable running to the instrument cluster. The cluster just snaps into a wire connector. I would think that somewhere in the tranny there is an actual gear. Maybe that is your problem. Stripped out, or skipping. I reread your first post, and I would say that it most likely is your BCM. It is located up in front of pass foot well. I have no experience with it, but have seen many threads about it. Radio and power windows stop working at same time Here's one. http://www.ls1.com/forums/f6/electrical-problem-165491/ Here's another one with some helpful pics from Smittro.
    If I let it idle with the AC on then it does it really bad (when I start driving). I'm thinking it's related to the temperature under the hood. That's why I just went ahead and ordered the ECM. I'll let you know if that fixes it.

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    I got the ECM and installed it. Very straightforward, easy install. Car drove a little funny the first couple miles while the computer was learning. Unfortunately, today is very cool outside so there's no way for me to know yet if it fixed the speedometer problem.

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    expensive tires az gt eater's Avatar
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    Keep us posted, im sure this will help someone else down the road.

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    Here's a video that shows what happens with the speedo needle. I made the video last month while driving down the interstate.

    http://img100.imageshack.us/img100/9810/47c.mp4

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    Bad news! The new ECM did not fix the problem. I may just take the car to a shop to have it fixed. No sense in continuing to guess at the cause of the problem. May take a little while though. Our other vehicle got hail damage this week and we just dropped it off for repair.

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    Update - after a few days, the new ECM started doing crazy stuff: the AC wouldn't work, the car ran bad and wouldn't start when hot. I pulled the new ECM and put the old one back in. Now the car is right back to where it was before - the speedo needle jumps but otherwise the car works fine. No returns on the ECM so I guess that's just money wasted.

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