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1998 V70 AWD Intermittent speedo failure

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  • 1998 V70 AWD Intermittent speedo failure

    The speedo works and fails intermittently on my 1998 V70 AWD Turbo wagon. Any clues as to possible cause and remedy would be appreciated.

  • #2
    Obviously, there is no old school speedo cable which means it's all electronic. Could be a few things such as wiring, speed sensor etc.

    speed sensor is a common issue.

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    • #3
      Is your ABS module original?
      If it hasn't failed yet, it's past due. Is your abs light on?
      Also, the dash modules are getting old and a smaller chance it could be that.

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      • #4
        The ABS light has been on since I bought the car 3 years ago. The module is likely original, but, not sure.

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        • #5
          2 failure points.
          1: module solder connections inside
          2: the wire harness with the 2 wires goes bad. The typical volvo insulation rot. Fix that and your issue will go away. Maybe.

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          • #6
            I read a post which suggested turning off and on the ignition to reboot the speedo. Tried it, and it worked. Have done this several times at a traffic light along the way, and it always reboots. Could the problem be related to the ignition?

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            • #7
              Honestly, let's look at your car:

              You state the ABS light is on
              You don't state any problems with the ignition switch

              therefore we know that there is a very good chance he ABS module is bad. Wheel sensors do go bad but modules always go bad eventually.
              We can assume that the ignition switch is functioning in all parameters except the unlikely possibility that it may be causing a speedo problem.

              The module can be rebuilt for about a 100 dollars (the guys that do it regularly do a much neater job and for only 100 bucks .why waste your time?)
              The ignition switch is around 65 dollars.

              another thing to think about, that ABS module just may have important functions beside the speedometer. Functions that you might really want to work well.

              both are easy jobs to replace.

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              • #8
                I'd like to recommend MidWest ABS. Easily found with web search.
                Plenty of good information. My ABS module was on the path Matt describes. The modules burn out because corrosion at the pins causes resistance, then heat, then failure. First, the ABS (and TRACS, if so equipped) light(s) come on. I never had speedo failure.

                I replaced my module this last January. I requested use of his Torx T5 socket, then returned it as he requested. The T5 socket I got at HF was too long and I couldn't reach the bolt heads at all. A 4mm socket will fit, but rounds the six tips on the bolt head. Mine were already rounded by the PO. Without the T5 socket, I would never have gotten the four bolts out. Also, a bit of butyl rubber in the socket keeps the bolt from falling out after extraction and during installation.

                To learn further how to remove and replace the module, I watched YouTube videos. A difficulty arose when removing the harness from the module that was not mentioned in the videos. It took me a while to figure out the sliding retainers on the each side of the main harness connector. No one mentions those on YouTube or in a forum. I asked Matt about this. He said "Nobody mentions that because they are supposed to move when the cover is opened. It means the mechanism, that is supposed to slide those levers in and out when the cover opens, is broken. The plastic gets brittle, and the cover breaks." After you open the cover to the harness, if the harness doesn't pull off, investigate whether the sliders that retain the harness have moved. If not, they just slide toward the engine compartment. I did use dielectric grease on the pins, and about the connector, at reassembly.

                Upon starting the engine, my ABS and TRACS lights were on. They remained on. I started the car and drove it several times, but never drove further than 3-4 miles. The lights remained on. After about 15 miles, still on. The next outing: Success. Lights off, no code on code reader.

                Best wishes.
                Last edited by Red Wagen; 09-04-2020, 05:41 PM.

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