Using my Snap on Tools to catch a problem

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  • eddie8
    Senior Member
    • Mar 2008
    • 273

    Using my Snap on Tools to catch a problem

    Hi guys.

    Sometimes you have to take more than one gun to a gunfight. This is a 2007 Chrysler Pacifica that had a phantom stalling problem. Trying to catch what was causing the engine to shut down while idling. This happened to be a bad cam sensor.

    Scoping and scanning
    Attached Files
    Edwin Hazzard
    Southeast Mobile Tech
  • maven
    Senior Member
    • Mar 2014
    • 269

    #2
    Why didnt you use your SnapOn shop light?

    Comment

    • eddie8
      Senior Member
      • Mar 2008
      • 273

      #3
      Its one of the few guns in my aresenal that I dont have!! I do have a snap on candle though but it was too windy that day.....
      Edwin Hazzard
      Southeast Mobile Tech

      Comment

      • eddie8
        Senior Member
        • Mar 2008
        • 273

        #4
        Guys...Here is where i lost my cam signal! Cam is channel 2 in green and crank is channel 1 in yellow. The Modis Ultra is very easy to use and gives a clear picture when you need it.
        Attached Files
        Edwin Hazzard
        Southeast Mobile Tech

        Comment

        • Witsend
          Banned
          • Nov 2012
          • 2942

          #5
          It be my luck after I post the picture and change the cam sensor, the truck problem would ultimately turn out to be a harness wire rubbing against something.

          Comment

          • diesel71
            Senior Member
            • Feb 2008
            • 921

            #6
            Nice work thanks for sharing.

            Comment

            • maven
              Senior Member
              • Mar 2014
              • 269

              #7
              Originally posted by Witsend
              It be my luck after I post the picture and change the cam sensor, the truck problem would ultimately turn out to be a harness wire rubbing against something.

              Thats why after you verify the issue is a sensor dropping out, you test the circuits before throwing a part at it...

              Comment

              • Witsend
                Banned
                • Nov 2012
                • 2942

                #8
                Thats why after you verify the issue is a sensor dropping out, you test the circuits before throwing a part at it...
                Reply With Quote
                Whether or not you are back probing the CMP sensor circuit at the connector of the CMP or the PCM with everything connected , if the signal wire were to chaffed through and intermitently ground , it's going to revert to a flat line what you are going to see on your scope when harness wire shorts.
                I would be more likely to condemn the CMP if the square patterns all showed up but don't reach near same voltage level amplitude as the Crankshaft sensor does or edges were rounded off or something. The best way to condemn the cam sensor I would think would be To disconnect the harness to isolate the CMP sensor from harnes and plug in a similar connector pigtail connector to attach probes to and crank the engine over and see if signal still drops out or not. In all honestty though I would probably slam a sensor and look a the harness and put plastic wiring conduit over harness at areas the harness looks like it may lay against and drive it .

                Comment

                • maven
                  Senior Member
                  • Mar 2014
                  • 269

                  #9
                  I dont follow, its been a long day.

                  You get that pattern from your testing of the CMP, and then you check to make sure Vref,Lref, and signal arent dropping out when issue occurs. That pattern just proves its the CMP system causing the issue. Not that its the CMP itself.

                  Comment

                  • Witsend
                    Banned
                    • Nov 2012
                    • 2942

                    #10
                    You get that pattern from your testing of the CMP, and then you check to make sure Vref,Lref, and signal arent dropping out when issue occurs. That pattern just proves its the CMP system causing the issue. Not that its the CMP itself.
                    Reply With Quote
                    I agree with you , I would at least attempt to inspect and wiggle the wiring harness,If I felt the drop out happened more while moving a section of harness, I would proceed to pinpoint testing of the 3 wires.
                    I admit I was totally wrong about being able to test the sensor, on car itself, using a 2wire terminal pigtail connector to see if it generates a voltage signal for the scope, LOL
                    Last edited by Witsend; 04-11-2015, 06:19 AM.

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