Speedometer went out

Discussion in 'Electrical & Stereo' started by scallahan04, Aug 9, 2016.

  1. scallahan04

    scallahan04 New Member

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    After having my 96 Cobra dyno tuned, my speedometer slowly started going out, and now completely doesn't work (which also took out the odometer). I don't 'think' the tuner killed it, because it lasted half the day once I left there, but I guess it could be an option.
    I have replaced the vehicle speed sensor (VSS) and also the toothed gear that goes onto the sensor (last one was chewed up) - no fix.
    So I went to O'Reillys and looked in one of their books/manuals they have for troubleshooting and found a few places to start. But this is where it gets confusing: It says to disconnect the harness to the VSS and with the ignition key ON, the reference wire should have 5 volts available. Then a different section right after that says to check for battery voltage.....which is it?!? Either way, I'm getting like 10.7V.
    I'm not the best at troubleshooting cars, so could use some assistance here. Any help is appreciated!! It's getting old having to use an app on my phone for my speed lol
     
  2. Frank.JD.Perez

    Frank.JD.Perez Well-Known Member

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    Correct me if I'm wrong, but it sounds like you're saying the mph isn't working right? How fast you're going not how far you're going as in mileage correct?
     
  3. scallahan04

    scallahan04 New Member

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    Both the speedometer nor the odometer are working.
    I've been doing some research since making this post, and making this reply might have my answer....both speedo and odometer work together on a gear inside the instrument cluster, could that have possibly just worn out and require replacing??? Found a repair kit for $25 and comes with both gears I would need.

    I just don't want it to be a wiring problem, I hate wiring lol
     
  4. scallahan04

    scallahan04 New Member

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    Could still use some help if anyone has any other insight on what the issue could be
     
  5. Frank.JD.Perez

    Frank.JD.Perez Well-Known Member

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    That's my question because if your mileage and trip stopped working then you need to replace your speedo gear inside the cluster. Super simple. If it's your actual speedometer like 20mph 40mph 60 etc then I have no idea
     
  6. lutter94

    lutter94 Well-Known Member

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    I believe the plastic odometer gear only affects the odometer. I had an issue with the speedometer, where it got (for lack of a better term) terets. Speed would jump around, and the needle would go all the way around and get stuck behind the peg. To fix that, I bought a cluster off of ebay, had a lot of miles on it so it was one of the cheaper ones. Pulled the speedo stepper motor out of it and installed it in mine, works great. I do have a speedcal on mine, its installed by the trans harness connector (firewall, passenger side) and had the whole speedo signal drop on me once. I had driven over some rough ass train tracks. Couldn't figure it out, replaced the VSS in the tranny, but after disconnecting/reconnecting the trans harness connector, my signal came back.
     
  7. scallahan04

    scallahan04 New Member

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    So I had the chance to pull my cluster off just now, and both the gears for the speedo and odo look good.
    So looks like I'm back at square one.
     
  8. lutter94

    lutter94 Well-Known Member

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    The VSS is just a magnetic pickup that counts teeth. If it's bad, you should be able to test it by unplugging the sensor, put jumpers on both of the pins, and touch them together on/off/on/off, really quickly. May have to have someone else in the car watching the speedo, see if it reacts at all. Or if you buy a new sensor, and rule that out. That only leaves it at checking continuity from the sensor to the dash....
     
  9. scallahan04

    scallahan04 New Member

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    The VSS has already been changed out.
    But my friend hooked up some scanner and everything can be read off it, and there was no speed signal coming out of the ECU. So he suggested to check and make sure the gear didn't actually move out of place inside the tranny.
    I believe the signal travels from tranny to ECU, then to the instrument cluster.
    So the scanner isn't showing a signal coming out, and not even sure it's getting to it.
     
  10. tachicardia

    tachicardia New Member

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    When you took the cluster out, did you happen to look at the printed circuit board in the back? One of the copper paths on the back of the speedometer could be broken/melted.
     
  11. lutter94

    lutter94 Well-Known Member

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    I would look into the trans harness connector, make sure all of the pins look good there.
     
  12. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    I'll preface with the statement that I have a 95 (OBDI) so that's where my experience is - having said that, it should be very similar for your 96.

    The speedo and tach get their signals from different wires on the ECU. There's a tach signal and a VSS (that the speedo uses). If both are not working, and you trust the scanner is correct in saying nothing is coming out of the ECU, the the issue is most likely either in the wiring leading up to the ECU (via the VSS) or the ECU itself.
     
  13. lutter94

    lutter94 Well-Known Member

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    His tach works properly, or at least he hasn't said that it doesn't.....lol
     
  14. mcglsr2

    mcglsr2 Well-Known Member SN95 Supporter

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    Ah, I interpreted "odo" to mean "tach."

    So....OP - what exactly doesn't work?
     
  15. lutter94

    lutter94 Well-Known Member

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    In the instrument cluster, the Speedometer and the Odometer (trip included) do not work. He has replaced the VSS in the transmission, and used a OBD2 Scanner (plugged in near your right knee I presume? Under the dash) to see if vehicle speed was being broadcast, it was not. Which leads the issue to lie in the wiring between the ECM and the transmission sensor.

    Install Guide for a Ford Racing Speed Cal is helpful. This PDF is helpful too - http://www.accutach.com/documents/terminatorengineharnessswapr1-3.pdf

    You can check continuity from the trans connector to the sensor on both of these wires.

    #679 is gray/black = VSS + Signal (PIN 15)
    #675 is pink/orange = VSS - Return (PIN 16)

    [​IMG]
     
  16. scallahan04

    scallahan04 New Member

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    You explained my issue spot on! Lol
    Where exactly is this connector? And am I shooting continuity to it from the VSS harness (on the tranny)?
    The harness on the tranny is a two pin, so where is this? On the ECU?
     
  17. lutter94

    lutter94 Well-Known Member

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    Lol, thanks! I had the exact same issue a year ago. Was just a connection issue in this connector.

    This connector is on the passenger side of the firewall. You really can't miss it. But yes you can check continuity from pins 15 and 16 and your VSS sensor on the transmission.

    Also found this - https://drive.google.com/file/d/178qzhIWL-P_jY2ZsMxb0Xdmjw7ao03-GMI5GXpQWjxXeD7Z8gPjWWv-KtX05/view

    You can check continuity from the VSS to these pins in the Computer (PCM)

    PIN 33 - VSS (-)
    PIN 58 - VSS (+)
     
  18. scallahan04

    scallahan04 New Member

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    Dude you're a lifesaver! I won't have time to mess with it until the weekend, but at least I have something to go with! And it very well could just be a bad connection at the computer, since it started right after I got the car tuned. Maybe messing with the chip inside the ECU too much rattled stuff around
     
  19. lutter94

    lutter94 Well-Known Member

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    Anytime! You need to make a welcome thread, post pics, you know the drill, lol.
     
  20. scallahan04

    scallahan04 New Member

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    Ended up changing the connector on the VSS. While shooting the wires it was shorted out; it was old!! So changed it and everything works perfect now!!