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    ABS Issue/Anti-Lock Light

    Hi All,

    Anti Lock light behaves normally on startup but kicks on intermittently/randomly during a drive when either of the rear sensors are plugged in. It doesn't seem to have rhyme or reason behind it. I've been driving around for a couple days with front sensors unplugged trying to figure out what behavior might trigger the light but no luck.

    Unplugged all the sensors and did spin test - Both front sensors set the light off and both new rear sensors do not. So this is what I'm working with -

    Two new GKN axles with abs rings
    Two new rear abs sensors
    Two abs modules (1 came with car, 1 in stock)
    New ABS Relay under dash
    New Speed Sensor in Differential

    Checked resistance on both rear sensors and got 1.08 ohms. I did not buy them for this problem, they are about two months old, but not sure how new OEM sensors that ohm out could be the culprit here. Replaced the relay and the module under the dash for under 40 bucks...Same behavior.

    Time to tap into the knowledge-base!!!

    From what I've read over the past few hours there isn't much to this. I have carefully examined all wiring underneath the rear section of the car for damage. I also inspected wiring to the pump under the hood, all looks pristine. There are two relays on the ABS pump itself but I don't see how they could be causing this. Signal from sensors go straight from sensors to module under dash. If the light turns off after starting it up but doesn't kick on from spin test then the module isn't getting a reading from the sensors. Do I need to buy two new sensors (again?) I pulled them from the hubs to take a peek and they look perfect. EDIT: I have successfully tested continuity and resistance from the connectors under the rear seat all the way to the large female connector for the ABS module under the dash.

    Just to pose a couple questions - Is there any component to this system that I might be missing? Or something in the innerworkings of the rear hubs that might be causing the sensors to get no reading? Could I have mucked something up during my recent bearing and axle replacement (this is how I ended up with two new sensors, pressing out the old wheel bearings without removing the sensors)? I did do the spin test after replacing the sensors and the test was successful at that time.
    Last edited by E30Bastard; 08-13-2019, 09:19 PM.
    "It wouldn't be there if it wasn't..." - Milton Berle

    1988 325iS - M20

    #2
    Buy two new sensors it is... Sent from my Pixel 2 XL using Tapatalk
    "It wouldn't be there if it wasn't..." - Milton Berle

    1988 325iS - M20

    Comment


      #3
      Did you ever figure out your issue?

      Comment


        #4
        Still waiting for two new bosch abs sensors to arrive in the mail. August 26th is the etd! Will update as soon as they arrive and I do another spin test. Sent from my Pixel 2 XL using Tapatalk
        "It wouldn't be there if it wasn't..." - Milton Berle

        1988 325iS - M20

        Comment


          #5
          Two brand new sensors arrived and got installed last night. Problem definitely not fixed. Light kicked on as soon as I started rolling forward. Back to square 1: Unplugged front sensors and went for a drive with both rear sensors plugged in. No light. Re-entered garage and light kicked on (random signal from rear channel i guess). Not sure what to do next here... From what I have read the only thing that would cause the symptoms I am having is a bad sensor or bad abs control module (I have 3 now after a 20 dollar ebay special and all 3 do the same shit). I will once again check resistance and continuity from the connectors under the rear seat to the abs control module connector. Any assistance would be greatly appreciated as this is the last thing on my checklist. Thanks Sent from my Pixel 2 XL using Tapatalk
          "It wouldn't be there if it wasn't..." - Milton Berle

          1988 325iS - M20

          Comment


            #6
            There's a relay in the immediate vicinity of the ABS module under the dash. The relay is black and usually right on top of the module. If possible, test it by swapping it with a known good one (from a car that isn't throwing the light) before dropping the $50 on a new one.
            Originally posted by kronus
            would be in depending on tip slant and tube size

            Comment


              #7
              Thanks for that idea, but it is already done. Bought a new relay before I bought the second set of new rear sensors, which I bought because previous r3v threads said not to trust resistance test on abs sensors and still same behavior. There are two relays on the pump itself that have not been changed but, again, according to jlevie this issue is bad sensors, bad wiring, or bad rear channel of abs module...all of which have been replaced or tested multiple times. Unless I am somehow missing an important detail when i installed the new pre-assembled axles with pre-assembled abs rings I am at a complete loss. About to buy another ebay abs module for 15 bucks as a hail mary... Sent from my Pixel 2 XL using Tapatalk
              "It wouldn't be there if it wasn't..." - Milton Berle

              1988 325iS - M20

              Comment


                #8
                Is there another component or signal to the abs system that would block it from getting signal from the rear? Thinking back after some good sleep I do remember for some odd reason the diff guy mentioned it might throw an abs light when i had it rebuilt a few months back (im guessing because of the speed rings and the speed sensor, somehow, idk tbh) but that never happened and my speedo is very functional and very accurate (plus i just replaced the speed sensor, which is obviously working, chasing down this abs light). Would/could the diff be the culprit? Sent from my Pixel 2 XL using Tapatalk
                "It wouldn't be there if it wasn't..." - Milton Berle

                1988 325iS - M20

                Comment


                  #9
                  Hail Mary ABS Module #3 arrived last night. Same behavior. Anti-Lock turns on when you turn the key, turns off when you start the car, and does not kick back on when either of the rear sensors are plugged in.

                  "It wouldn't be there if it wasn't..." - Milton Berle

                  1988 325iS - M20

                  Comment


                    #10
                    kill it with fire
                    Simon
                    Current Cars:
                    -1986 BMW 325e & 1968 Datsun Roadster 2000
                    Previous Car Count : 21 ... and climbing...
                    Originally posted by Melon
                    Let it be known to all. Simon fucking keeps it real.

                    Comment


                      #11
                      All right...bought the two relays on the ABS Pump itself. Now all three relays of the ABS system have been replaced with OEM new relays. Problem still exists.

                      All the parts are new or replaced except the pump itself. The wires have been tested. Any help at all would be greatly appreciated
                      "It wouldn't be there if it wasn't..." - Milton Berle

                      1988 325iS - M20

                      Comment


                        #12
                        Are the front sensors new as well? Maybe one of the pulse rings is different on one of the axles?
                        sigpic

                        Comment


                          #13
                          Andrew, Thanks for the response. Front sensors look to be as old as the car but spin test works on them. Anti lock kicks on immediately when moving forward if I have either of the front sensors plugged in solo. As for pulse rings - they are gkn oem rear axles matching the manufacturer model number on realoem- GKNLoebro BMW 33211226901 or GKN-300693. All 4 new rear sensors are bosch oem as well. Sent from my Pixel 2 XL using Tapatalk
                          "It wouldn't be there if it wasn't..." - Milton Berle

                          1988 325iS - M20

                          Comment


                            #14
                            This is what they look like out of the car (pic 1 from fcp euro, pic 2 shows how it works for idiots like me). The pulse/reluctor ring looks to come pre-installed...I have one faulty gkn axle out of the car. Here's a pic of that too: Sent from my Pixel 2 XL using Tapatalk
                            "It wouldn't be there if it wasn't..." - Milton Berle

                            1988 325iS - M20

                            Comment


                              #15
                              Try ohm the sensors circuit from the ABS computer.

                              All your tires the same size? Air’d up also.

                              All sensors new?

                              Wheel bearing play front or rear?
                              sigpic
                              1999 BMW 318Ti/M Hellrot Msport DD/Fun car
                              1/2 1987 BMW 325is/M Future Spec e30 (track prep'd)
                              1994 530It/A Alpinewise III Traded out
                              1988 BMW 325ix/M Diamond Schwartz Recently sold :/
                              1986 BMW 325e/m Bronzit Beige Metallic

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