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Speedometer stopped working? How to replace your Vehicle Speed Sensor (VSS) - 3rd Gen

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    Speedometer stopped working? How to replace your Vehicle Speed Sensor (VSS) - 3rd Gen

    I looked all over for how to do this, and after some trial and error and a visit to the parts store I figured out how to do this, and what part to use.

    My speedometer stopped working yesterday all of a sudden. Pulling the negative cable did nothing, so I assumed it was either a speedometer cable or the VSS. Turns out these cars don't have the cable like I'm used to with older cars, so VSS it is! Note that at the time, the CEL did not come on. It only came on after going to the parts store, oddly. The CEL code will likely be P0500 but can also be P0501, P0502 and P0503.

    Depending on if you have an automatic or MTX, the parts are different.

    Part number for the Automatic is SU6385 and looks like this:



    Part number for the MTX sensor is SU6386 and looks like this (notice the blue gear, that's one of the main differences as well as the placement of the bolt)



    Make sure you order these online because Autozone's price is about 30% more.

    2) To remove this, you will need to take out the following (note that EVERYTHING takes a 10mm socket which is awesome. I suggest 2 or 3 long extensions though):

    Battery
    Battery harness (the entire thing, even the part the battery sits on)
    Air intake hose, just remove the whole thing. You can keep the filter box in, just take the top off.

    Standing at the driver's side wheel, look down near the back of the tranny.



    You should see a bracket making a kind of a U shape (or a backwards C shape if you're looking from the front) with two bolts. The bracket goes around the sensor, you should be able to see the electrical connector going into it. It's straight up and down. The automatic would have the connector off to the side. Remove the two bolts and the bracket, otherwise you won't be able to get the damn sensor out and you'll just get angry.

    Remove the 10mm bolt near the sensor after removing the electrical connector. The connector can be a little tricky to get out. After removing the bolt, grip the sensor as well as you can and turn it back and forth a bit to loosen it while pulling up. Eventually it should pop out. Put in the new sensor (make sure to lube it up with some ATF before placing it back in) and put everything back together. Now enjoy a working speedometer again!

    #2
    is the VSS connector the same style connector between the Automatic and Manual transmissions? Meaning - do they have the same plug (3-pin?)

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      #3
      Originally posted by ihone View Post
      is the VSS connector the same style connector between the Automatic and Manual transmissions? Meaning - do they have the same plug (3-pin?)
      The VSS for the MTX is 2 pin, the VSS for ATX is 3 pin. I'm guessing they did this to make sure you didn't try to plug in the wrong part, not sure. But they're obviously different parts as the MTX has the plastic gear on it.

      Fun fact - when the VSS goes, so does your digital odometer!

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        #4
        I never got my speedo working - and now I'm thinking it's about time to get it done. After doing the KL swap (kept it auto for a bit, until I blew the atx) and after swapping the KL auto to a manual trans - the VSS plug on the trans has a speedo gear (so does the diff), and has 2 prongs. The VSS plug from my atx wiring harness in the P5 has 3 prongs.

        Any idea on how to make this actually work? I'm stuck honestly.

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          #5
          My only guess would be to get the connector from a junked 3rd gen and rewire it. The ATX has 2 wires going into the connector, right? My MTX has 2 wires into, so if that's the case just match them up, connect them securely and plug in the new connector into the new MTX VSS.

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            #6
            ATX connector has 3 wires, MTX has 2. I have a connector, and I've even taken the liberty of splicing some generic wires into that connector - and running them directly to the speedo input wiring for the dash. No go......weird, eh?

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              #7
              I'm not sure how you'd do it then - I'd guess only 2 wires would need to be connected. You'd have 3 combinations of wiring using only 2 of the wires. If that doesn't work then with my limited knowledge on this, I'm stumped. We'd need a Mazda mechanic on this question, but it's definitely a good question as I'm sure there's others who have swapped auto for manual.

              Edit: Maybe also try connecting 2 of them together and one by itself in a few different combinations?

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