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Speedo stuck at zero or buried past 100

Discussion in 'Chevy Express Forum (GMC Savana)' started by carp, Jun 13, 2012.

  1. carp

    carp New Member

    What causes the speedo to act up all of a sudden? If I pull out and stay under say, 25mph, it stays on zero......once it comes off zero, it reads way high and will eventually go past 100 and stay there even if I slow down. I also have the vibrating fuel guage needle "hummingbird needle" and the oil pressure is all ratchety. Im assuming the oil pressure is a sending unit??? Is the speedo problem a Vehicle Speed Sensor??
  2. the phantom

    the phantom Active Member 2 Years ROTM Winner Gold Member 1000 Posts

    What year vehicle have you got?? GM had issues with the I believe 03-05 Instrument Cluster stepper motors, specifically the spedo. There was a time and mileage sensitive recall on them like 7 years and 70,000 miles or under.
  3. ChevyHD

    ChevyHD Rockstar 100 Posts

    Most likely need to replace your stepper motor if it is the 03-05 cluster like mentioned above. Its rather easy, just need to be able to unsolder and solder in the motors. You can get a pack of motors off of ebay for about 50 dollars.
  4. carp

    carp New Member

    Its a 1998 GMC Savana 1500, 5.7 with 4L60E. Just replaced the only "speed sensor" in the trans tailshaft.....IT DID NOTHING. I thought it would at least turn out my rear anti-lock light. ANY HELP?....The speedo seems to read double the actual speed.
  5. carp

    carp New Member

    Does this van actually have rear ABS? There are no rear wheel sensors or any sensors on the rearend housing but the ABS code is showing a difference in wheel speed from front to rear. Also.....Cruise Control doesnt work now that the speedo is acting up. THE VSS HAS BEEN CHANGED & IT DID NOTHING.
  6. moogvo

    moogvo Epic Member 5+ Years 1000 Posts

    You have a ground problem to your cluster.
  7. carp

    carp New Member

    A ground problem? Why no cruise control all of a sudden? If I plug in my scan tool that reads live data, I am getting a vehicle speed signal.....where is that coming from?.....the vss right?.... So, why the constant anti-lock light?.....does this van even have rear anti-lock??..... I'm Frustrated!!
  8. carp

    carp New Member

    Could it be the sensor wheel itself inside the tailshaft housing?....the one that the vss reads??
  9. moogvo

    moogvo Epic Member 5+ Years 1000 Posts

    No. You either have a bad ground or a short. Check the smaller wire from the negative side of the battery and make sure it is attached at both ends. That is your starting point. If you are getting the correct readings with the scan tool, then the sensors are fine. Your computer tells the cluster what to show. There is a communicarion problem between the computer and the cluster. Most likely a ground problem.
    Last edited: Jun 16, 2012
  10. carp

    carp New Member

    Everything checked out. The oil, gas and speed gauges act up. The volts and temp are fine. If you flick the needles individualy, the speed, oil & gas needles will move very, very freely......oil & gas spin completely around many times......the gauges acting up. The temp and volts needles have resistence and move back when rotated.... So, I'm thinking 3 bad motors. I was going to replace all 5.

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