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Anonymous Posted on Apr 11, 2011

The speedometer in my 2002 Chevy 2500HD pickup varies in by +/- 5mph while traveling on flat smooth pavement. I have found that if the truck is using throttle it will read +5 and if it is more coasting, it will read -5. To put it another way, if I press the accelerator slightly the speedometer will immediately gain 5mph, whereas, if I release it slightly it will lose 5mph right away. It does this quickly, before the vehicle could actually have time to gain or lose speed. I replaced the speed sensor in the transmission thinking that was the problem, but no joy. It causes the cruise control to continuously "hunt" to maintain speed. Can you tell me what might be the problem?

  • 3 more comments 
  • Anonymous Apr 12, 2011

    Thanks. I called instrumentclusters.com this morning. They say it'll cost $75 to fix. So, I'll mail it to them and let you know if that was the problem or not when I find out one way or the other.

  • Anonymous May 07, 2011

    Got my cluster back from Southern Electronic (www.instrumentclusters.com). They say that they "Added fluid to the speedometer movement. All functions checked, OK."

    I re-installed and took it for a spin. Same problem! It works no better now than $100 ago. Seems the problem is not the cluster or speedometer or speed sensor.

    Want to take another shot at it?

  • Anonymous May 07, 2011

    Looks like I posted that in the wrong place. Here is my reply again...

    Got my cluster back from Southern Electronic (www.instrumentclusters.com). They say that they "Added fluid to the speedometer movement. All functions checked, OK."
    I re-installed and took it for a spin. Same problem! It works no better now than $100 ago. Seems the problem is not the cluster or speedometer or speed sensor.
    Want to take another shot at it?

  • Anonymous May 07, 2011

    I think they charge $50 just to hook it up. Can I do the same with one of those OBDII code scanners? ie., www.google.com/search?q=OBDII ? I've been thinking about getting one of those anyhow. If not, what equipment is needed? Can you point me to a web site with a diagram of the different components that make up the speedometer system for my truck?

  • Anonymous May 07, 2011

    How do I request a 2nd opinion?

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1 Answer

Marvin

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  • GMC Master 85,242 Answers
  • Posted on Apr 11, 2011
Marvin
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Hello
This problem is caused by a defective instrument cluster and it must be send out for updated parts and repair of defects in the design. Although the instrument cluster in this truck uses what looks like analog instruments it is actually digitally controlled by a small computer inside the cluster assembly, this same computer it seems sends the signal to the cruise control as well, so if the speedometer needle is getting a faulty signal then the cruise will act up as well. There are many places on the Internet that can do this repair, you are not stuck with the dealer who will 2X the cost of the repair of the cluster to you (capitalization in all it glory). These companies will send a special box to ship the cluster in and provide full instructions on removal.
Below is one such link to a cluster repair service, give them a call about your particular problem.

http://www.instrumentclusters.com/

  • 2 more comments 
  • Marvin
    Marvin Apr 12, 2011

    Great, I'm as sure as I can be without coming to your house that the problem is the cluster processor unit.

  • Marvin
    Marvin May 07, 2011

    You need to consult a qualified GM dealer and have them hook up the appropriate equipment to see what signal is being lost and where, I can only offer information based on similar problems. Sorry can't do that kind of hands on diagnosis over the keyboard of this computer.

  • Marvin
    Marvin May 07, 2011

    You will need a GM Tech II scanner (or another full function tester like it) to access the data stream.

  • Marvin
    Marvin May 08, 2011

    I can't do what you ask as far as knowing the procedure for getting a 2nd opinion, but if you contact the fixya support team at the email address below they will. I have also sent an email to Lauren Chang who is the head person of the web site as far these kinds of issues go. Thanks



    [email protected]

    [email protected]

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