2008 Town And Country Abs Component Test

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  • greasybob
    Senior Member
    • May 2008
    • 1590

    2008 Town And Country Abs Component Test

    I recently had a 2008 Chrysler Town and Country with codes C1020 and C102B. I replaced both Rear ABS sensors and cured the problem. After the repair I wanted to check for a speed sensor for a signal with the scope. According to the component test the module supplies the signal with 12 volts and there should be a square wave on the return wire of about 1.5 volts. What I found however was that the return wire never came off of 0 volts and the supply voltage wire was showing a sqare wave drop in voltage of about half a volt. I tried back probing the return wire several times but could never find a signal while the tire was spinning but never had a problem finding the signal on the supply wire. As you can see in the scanner shot all the sensors are working. The other thing I noticed is that the codes set with the old sensors without the vehicle moving wihich should indicate that there should be a voltage drop or resistance or amperage test for these sensors. Is the component test here wrong ? Anyone else try to test these sensors ?
    Attached Files
  • Crusty
    Senior Member
    • Dec 2007
    • 2450

    #2
    Hi Bob
    It appears to me that the carrier voltage is varying the amplitude by about .8 to 1.6 volts based on the screen showing the 12V signal.
    Remember the European company that owned Chrysler in 2008 had a hand in developing the technology used so the semantics their engineers use might not be translated quite the way we understand the English language.
    I don't know, just surmizing from what the description says and the screen shot.
    It certainly is a little "fuzzy" (that IS an engineering term used, kinda like "Polish Logic" if ya know what I mean)....
    Based on the connector view and the descriptions of the terminals, I would certainly expect to find something on the pin #1 described as WSS SIGNAL, rather than the 12V supply pin #2.
    Last edited by Crusty; 09-09-2011, 01:17 AM.

    Comment

    • Skip
      Super Moderator
      • Apr 2008
      • 605

      #3
      Good stuff Bob. I'll look into this further and get back to you.

      Comment

      • Trindaddy
        Senior Member
        • Jan 2010
        • 339

        #4
        Thats not much of a "square" wave Greasy, looks more like a noisy voltage. Was this taken while running or on the charger? I know you know your stuff, but you must have had the scale set wrong or something, bad connection, schematic wrong?

        Comment

        • Orevin
          Senior Member
          • Aug 2010
          • 1110

          #5
          Maybe TS should mention the type of WSS installed on this van. Given the troubleshooter description, these are active wheel speed, or magneto-resistive, sensors, sensing a change in voltage AND amperage. A micro amp probe should be used if you want to look at the signal on a scope, as the current flow is very low, similar to what you would see on AFR sensors.

          Here are some articles on active speed sensors:




          -Kai-
          Chicago, IL

          Comment

          • Crusty
            Senior Member
            • Dec 2007
            • 2450

            #6
            Originally posted by Orevin
            Maybe TS should mention the type of WSS installed on this van. Given the troubleshooter description, these are active wheel speed, or magneto-resistive, sensors, sensing a change in voltage AND amperage. A micro amp probe should be used if you want to look at the signal on a scope, as the current flow is very low, similar to what you would see on AFR sensors.

            Here are some articles on active speed sensors:




            Good stuff.

            Thanks for the articles Kai

            From a quick glance it looks like the TS does need to be corrected so the testing is clarified and not just click-copy-paste from a previous YY/MM/MM
            I wonder how far BACK the correction needs to go and if it will go back at all.

            Whether information is MISSING or information is MISLEADING, either way it's broken.

            Comment

            • greasybob
              Senior Member
              • May 2008
              • 1590

              #7
              The Town and Country was still here late this afternoon so I decided to bring it in and test it again, this time I have the test on video, Trindaddy was right, I had a bad ground the first time, got that cleaned up but the only difference is a cleaner signal. http://www.youtube.com/watch?v=QFMe70f9ht4

              Comment

              • Skip
                Super Moderator
                • Apr 2008
                • 605

                #8
                Chryslers web site does not give any kind of description as to how the speed sensors work on the mini van but they do for several other vehicles of the same year with the same ABS system.

                When a valley of the tone wheel is aligned with the sensor, the voltage signal is approximately 0.8 volts and a constant 7 mA current is sent to the ABM. As the tone wheel rotates, the tooth shifts the magnetic field and the IC enables a second 7 mA current source. The ABM senses a voltage signal of approximately 1.6 volts and 14 mA. The ABM measures the amperage of the digital signal for each wheel. The resulting signal is interpreted by the ABM as the wheel speed.

                However, as Bob has shown, this information is not completly correct. I believe him on reputation alone. I am still trying to determine how big this issue is. The fault is mine, blame and/or shoot me.

                Comment

                • crackerclicker
                  Senior Member
                  • May 2008
                  • 400

                  #9
                  please forgive me for always linking to autonerdz, but these are the only examples i have to share with you for active wss.

                  Comment

                  • Crusty
                    Senior Member
                    • Dec 2007
                    • 2450

                    #10
                    Originally posted by Skip
                    Chryslers web site does not give any kind of description as to how the speed sensors work on the mini van but they do for several other vehicles of the same year with the same ABS system.

                    When a valley of the tone wheel is aligned with the sensor, the voltage signal is approximately 0.8 volts and a constant 7 mA current is sent to the ABM. As the tone wheel rotates, the tooth shifts the magnetic field and the IC enables a second 7 mA current source. The ABM senses a voltage signal of approximately 1.6 volts and 14 mA. The ABM measures the amperage of the digital signal for each wheel. The resulting signal is interpreted by the ABM as the wheel speed.

                    However, as Bob has shown, this information is not completly correct. I believe him on reputation alone. I am still trying to determine how big this issue is. The fault is mine, blame and/or shoot me.
                    Naaaaaw, my shotgun isn't loaded right now....

                    The 0.8 volts and the Integrated Ciruit (IC) chip in the sensor (???) creating the second voltage that would double to 1.6 volts, and then the 7ma doubling to 14ma kinda makes sense. Something I am wondering about is....is the voltage a DC voltage or an AC voltage?? Could that be why Bob couldn't pick up a voltage signal on the "signal" wire because the machine was on a scale that couldn't pick it up??

                    The information you just posted should be worded that way in the description in the scanner & scopes. Where it states that the module is reading the 7ma or the 14ma would have made the person looking at it check for something other than just a DC voltage

                    The small details make the big difference as to whether we're diagnosticians or not. Without COMPLETE information ( including missing pids Jay) we can get lost chasing our tails until stubborness and perseverance allows us to figure out what is really going on in ANY system.

                    Thanks for finding it Skip.

                    Comment

                    • greasybob
                      Senior Member
                      • May 2008
                      • 1590

                      #11
                      The link that crackerclicker posted seem to show what I found, the voltage squarewave is on the supply wire which shows battery voltage. It seems the sensor does little more than provide enough of a load to pull this voltage down about half a volt, thus the amp load. Remember in my video I showed that the wire marked wss had less than .5 ohms resistance to ground. It would seem rather unlikely that you would get any measurable voltage on a circuit grounded like that without considerable amperage, enough to melt the wire.

                      Comment

                      • Skip
                        Super Moderator
                        • Apr 2008
                        • 605

                        #12
                        Looks like DamnearChrysler uses a couple different types of sensors. I have tested the .8-1.6 square waves on different cars. I even used an analog meter just to try it. Having been owned by Benz for 10 years, the quality of their service information has dropped like a rock.

                        Comment

                        • Crusty
                          Senior Member
                          • Dec 2007
                          • 2450

                          #13
                          Originally posted by greasybob
                          The link that crackerclicker posted seem to show what I found, the voltage squarewave is on the supply wire which shows battery voltage. It seems the sensor does little more than provide enough of a load to pull this voltage down about half a volt, thus the amp load. Remember in my video I showed that the wire marked wss had less than .5 ohms resistance to ground. It would seem rather unlikely that you would get any measurable voltage on a circuit grounded like that without considerable amperage, enough to melt the wire.
                          Sorry...I don't "youtube" LOL

                          So what you're saying is the 0.8 to 1.6 volts is DC and it "rides" on the 12 volt B+ wire. That makes the label or indication of "signal" on the other wire incorrect or misleading.
                          With the info Skip posted, the module is really looking for the 7ma and 14ma change to get it's frequency from, which indicates the speed of rotation.
                          Attached Files

                          Comment

                          • Crusty
                            Senior Member
                            • Dec 2007
                            • 2450

                            #14
                            Originally posted by Skip
                            Looks like DamnearChrysler uses a couple different types of sensors. I have tested the .8-1.6 square waves on different cars. I even used an analog meter just to try it. Having been owned by Benz for 10 years, the quality of their service information has dropped like a rock.
                            It can't have dropped very far.......LOL
                            I was speaking to a 30 year veteran of Chrysler dealers about 15 years ago....."the Chrysler manuals leave a little bit to....uh....the imagination" LOL

                            Comment

                            • Crusty
                              Senior Member
                              • Dec 2007
                              • 2450

                              #15
                              Searching the Dodge wheel speed sensors, there was some information in the 2005,2006 & 2007 model years but the 2008 and newer said pretty much that there was a tone wheel (NSS)..

                              ""The ABM sends 12 volts to power an Integrated Circuit (IC) in the sensor. The IC supplies a constant 7 mA signal to the ABM. The relationship of
                              the tooth on the tone wheel to the permanent magnet in the sensor, signals the IC of the sensor to toggle a second 7 mA power supply on or off. The
                              output of the sensor, sent to the ABM, is a DC voltage signal with changing voltage and current levels. The ABM monitors the changing
                              amperage(digital signal) from each wheel speed sensor. The resulting signal is interpreted by the ABM as the wheel speed.""

                              I asked my Chrysler parts dealer to check the sensors & they range from 2004 to 2012 model years for application so i have no explanation for the lack of published info from 2008 & up.
                              Skip's right, the information HAS dropped like a rock.

                              Comment

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