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Speedometers and Scan Tools 850

posted by  Mike Brown on  Mon Oct 8 12:07 CST 2007
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last visit: Sat Dec 8 20:06 CST 2007
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Will a basic scan tool (i.e Actron ~ $100) read P-0500 series codes and higher? I have a friend with a malfunctioning speedometer and odometer (both work intermittently). I misdiagnosed the issue as the electrical portion of the ignition switch, but the problem persists after replacement.

I know the ABS computer has failed - and is destined to be sent to Victor Rocha. I've read is past posts that this can be the source of this issue, but I'm hoping to diagnose the problem fully before I continue swapping parts.

I'm looking at either pulling the cluster and checking the line voltage, or pulling the air cleaner assembly and checking the speed sensor right at the transmission. Neither has been much fun in the past, and I've often contemplated buying a basic scan tool, but I'm not certain it would help with this issue unless it reads the relevant codes.

Any thoughts?







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    Speed Sensor - Klaus? 850

    posted by  Mike Brown on  Tue Oct 9 13:22 CST 2007
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    last visit: Sat Dec 8 20:06 CST 2007
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    Greetings-

    While I wait for my e-5 torx bit to be shipped (if folks don't already have one, you might want to search before you need it) to remove the ABS controller, I thought I might give the speed sensor a little more attention. I understand this is located on top, near the PNP switch. Is this accurate? Is there an easy way to test this component?








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      Speed Sensor - Klaus? 850

      posted by  vitor on  Sun Oct 14 11:23 CST 2007
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      last visit: Sat Dec 8 05:01 CST 2007
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      On 96-97 850 models and all 70 series, the speedometer is driven by a signal from the ABS unit.
      The signal is a square wave and depending on the frequency, the speedometer reads the speed.
      When the ABS unit loses more than two wheel speed sensors, the speedometer will stop working. The ABS unit cannot calculate the speed anymore. This happens when you drive with a defectve ABS unit for a long time.
      When you remove the ABS unit, you lose the speedometer.

      Read more about it here.
      http://home.earthlink.net/~vicrocha/Volvo_Parts/Volvo_V70_ABS.htm








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    Speedometers and Scan Tools 850

    posted by  someone claiming to be gwen on  Mon Oct 8 13:58 CST 2007 [RELATED]

    I just know that when the volvo dealer replaced my rear main seal some years ago, the mechanic didn't plug the speedometer plug back in under the car in the transmission bell housing. I got home and jacked the car up and found the plug hanging there. Might be something to check.








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      Speedometer Sensor - Test? 850

      posted by  Mike Brown on  Mon Oct 8 15:15 CST 2007
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      last visit: Sat Dec 8 20:06 CST 2007
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      Thanks Gwen-

      I thought the sensor was on top of the engine so I did not even try looking underneath.

      Assuming all is connected - is there a procedure for bench testing this sensor?

      Mike








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        Speedometer Sensor - Test? 850

        posted by  kshaw on  Fri Oct 12 15:54 CST 2007
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        last visit: Wed Oct 29 13:11 CST 2008
        [RELATED]

        I have an Autoenginuity laptop scanner that will read many of the sensors while you are driving and display the readings. It will display the speed sensor readings. If you can use something like this, you could detect whether you have a bad speed sensor or not. If your speedometer fails while the sensor is still giving good readings, then you have a wiring problem or a bad speedometer guage. http://www.autoenginuity.com/

        --
        1998 Volvo S70







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