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  1. #11


    I dont think you can do that with the buffer thing in there. Either way I dont get why the ECM has to be there to make the speedo work. The only wire going to it that has anything to do with it is a VSS wire that goes from the cluster to the ECM then there is no output from the ecm of the vss. So with it just sitting at 10 mph i am kinda at a loss. I was told that the ecm being disconnected would make it not work. It makes no since seeing as it gets power else where and signal from the sensor comes from the sensor to the speedo.

    - - - Updated - - -

    So after some hair pulling I got it. My speedo works great now and here is what I did....There is a brown/white wire that goes to the ECU from the cluster and I cut it from the ECU connector and grounded it. It is a VSS wire in to the ECU. I have Mitchell and in the schematic it shows only two wires from speed sensor to cluster and then one from cluster to ECU with a tie in to the brown/white going to the rwal module. I figured whats worst that can happen right. Someone has to have done this before but for some reason didnt share it so there it is. After I touched that wire to ground with the key on the speedo went to zero. Drove it with it grounded and barely moved and seen it working....

  2. Thanks bradyjames thanked for this post
  3. #12
    Jr. Apprentice
    Join Date
    Jul 2010
    Sacramento, CA


    88k2500 - do you have any photos of this procedure...I am having a similar problem with my speedo not working. Sometimes it works, sometimes it doesn't... I would like to fix it since it's been going on 2 years now....

    thank you.
    Brady James
    1989 GMC Sierra c2500

  4. #13


    80 8K, why don't you throw a mechanical fuel pump in there for redundancy backup? That way when the big ECM hits you might still be able to drive. I do know if a few guys that of been doing this after they turn it over to carburetion normal aspirated. But then of course they do have some pretty deep bunkers and most all will tell you guns very bad for you. And scary to but you see go filters Distributors part plugs tires patches things like that store right next to the ammo cans. Not me mind you Gunzer scary!

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