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ABS not working after chassis harness swap

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  • ABS not working after chassis harness swap

    guys, i have owned my car for 18 some months now. i bought it from a guy who was installing a new chassis wiring harness due to many "gremlins". car was running when i bought it, but many of the accessories were not functioning. i have since gotten almost everything working except for a few things like ABS, power locks, and the interior light timer.

    saturday i started digging into the ABS problem, which is the dash ABS light is always on and ABS is not functioning. i looked for the well-known ABS over voltage relay, but cannot find the harness connector anywhere. my car is a 12/87 build date so it SHOULD have one. i dug into the paperwork left by the previous owner and found an invoice dated 5/3/04 for harness 61 11 1 394 058. i dug out the old hacked up harness and found part number 61 11 1 385 532 on a sticker on the fuse box. looking at the ETK for US cars, it seems 532 ended and was replaced by 058, which eliminated the over voltage relay. interestingly enough i also don't have any wiring for the glove box light and switch but not sure why.

    in testing the ABS computer connector i have the following:
    pin 1 - 0v
    pin 15 - 12.7v
    pin 29 - 12.7v
    pin 25 - 12.7v w/ brake pedal depressed
    pin 10 - ground
    pin 20 - ground
    pin 34 - ground

    tests at the ABS unit connector under the hood shows:
    pin 6 - 12.7v
    pin 12 - 12.7v
    pin 7 - 12.7v
    pin 10 - 0v

    all tests done with the key in pos II (or run)

    wheel sensors check out ok for resistance; all 4 somewhere just north of 1000 ohms.

    this all leads me to believe that my only problem is the ABS computer not getting a turn on signal at pin 1 and the pump not getting a turn on signal at pin 10. i've read posts from John about an 88 engine harness in a 90 car, where he installed a pin at location 20 in C101 and tapped into the heavy gauge red/white wire at the middle of the firewall. this would seem to apply in my case. also, does anyone know the part number for a C101 pin? i don't think the dealer is smart enough to find one without it. i might try pulling one from a parts car but these pins are pesky and hard to remove. might be easier to buy a new one.

    in looking at my C101, i don't have pins at 3, 12, 17, and 20 (engine side) and 3, 12, 17 (harness side). so it seems it is as simple as adding a pin to the engine side of c101 and splicing it into the red/white wire. i'm guessing scotch-loks are not recommended here. any tips on creating a professional type splice? i'm handy with a soldering iron and heatshrink tubing, but only really when creating butt connections.

    i hope all this makes sense. i think i've done the detective work and come up with a solution, but i' also wondering about how the over voltage protection is implemented on the mid-89 and later cars? was it part of the ABC computer? is there a different part number for those cars? i have two ABS brains, one from my car and one from a 325 (don't remember the year) and both have the same Bosch p/n 0 265 103 004.

    i also posted this to the SIG but know not all of you are on there and this is also good for the s14.net archives.
    James
    sigpic

  • #2
    FWIW, my 3/87 production car has the external ABS relay. My older, in ownership, but newer 11/87 production car did not.


    Nick

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    • #3
      digging through the ETK, i found a couple part numbers for the C101 engine harness side male 2.5mm pins:
      61 13 0 007 452 - comes with wire pre-crimped
      61 13 1 376 191 - just the bare uncrimped pin

      both these ends are sized for 16-20 AWG, which fits right with the 18 AWG spec'ed in the ETM diagram

      now do i get super-anal and cut a wire out of a parts car or my old harness of the correct gauge AND color (RD/YL)? :idea:


      i'm still unclear on the ABS computer. can someone with a 89+ car chime in w/ the part number of their computer? i'm not too worried about it, as i have a second unit in case i blow mine up [done]
      James
      sigpic

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      • #4
        Originally posted by Nikos
        FWIW, my 3/87 production car has the external ABS relay. My older, in ownership, but newer 11/87 production car did not.


        Nick
        ok, that's wierd and doesn't track with the service bulletins or anything else. you SURE it was an 11/87? did it have the chassis harness replaced at some point?
        James
        sigpic

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        • #5
          Isn't there a relay near the steering column under the dash. It has a silver cover. There is a very thin wire that always burn. The relay is not cheap. So, what most "klugers" will do is to weld a larger wire. I did it and it solved my ABS problem...


          [email protected]

          1969 2002 racecar
          1989 M3 racecar
          e39 Touring

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          • #6
            Originally posted by LeeVuong
            Isn't there a relay near the steering column under the dash. It has a silver cover. There is a very thin wire that always burn. The relay is not cheap. So, what most "klugers" will do is to weld a larger wire. I did it and it solved my ABS problem...
            the silver relay you mention is the over voltage relay. i have that relay, but no connector on the wiring harness to plug it into

            all cars up until 1/89 had the relay. after that bmw eliminated it and supposedly incorporated the protection into the abs computer itself
            James
            sigpic

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            • #7
              bringing this back up. i have a new male pin for the C101, but haven't had the time to hook it up yet.


              can anyone with a mid-89+ car chime in with the part # off their ABS brain?
              James
              sigpic

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              • #8
                It has been a while since I messed with that, but
                you have the reverse situation than what I did.

                I had a non-relay ABS, so my wiring from the
                abs computer up into the C101 had a connection for pin 20.
                however, I did not have a wire running from the
                battery block over to the C101 harness side.
                (that is as far as I remember -- I remember I posted my results
                on the SIG, I assume that is what you read).

                There are other differences between a 90 harness
                and a pre-90 harness as well. e.g. regarding unloader
                relays due to a lack of ground onto the starter motor
                from C101, the OBC and the extra little harness connectors
                "fahrzeug kabelbaum" (rpm fuel etc )that some of the cars had.

                You probably read that in my post though. I have it written
                down somewhere if you cant find it...

                John

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                • #9
                  actually our situations are the same. my chassis harness is from early 89, but the engine harness is rom 12/87. we just arrived at the same end result by different paths; you putting an older engine harness in a newer car, me putting a newer chassis harness in an older car.

                  maybe there's some difference in the euro harnesses because the only thing that doesnt work is the abs. my problem now is i don't have over voltage protection because my abs pump and brain are the older models
                  James
                  sigpic

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                  • #10
                    UPDATE:

                    finally got the time to mess with my ABS. as i said, i purchased a new C101 pin from the dealer. i crimped and soldered it onto a length of 18 AWG wire and installed it in the engine C101 connector at postion 20. i then ran the wire along the firewall and over to the battery junction terminal behind the coolant reservoir. i spliced and soldered it onto a thin red/white wire that is connected to both the main and fuel pump relays simulating how the 89+ engine harnesses look.

                    started the car up, blipped the throttle and the ABS light turned off for the first time in almost 2 years of ownership! i took it for a run up and down the street seeking out any dirt or loose rocks to test the ABS.

                    IT'S ALIVE!!!!
                    James
                    sigpic

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                    • #11
                      congrats!!

                      greg,
                      garber's

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                      • #12
                        Great Work!! It pays to take your time, be patient, and thorough! Now the important question, did you reward your efforts with a nice cold German beer?



                        I think it is truly a love/hate thing with older cars. The things we hate about them are the finiky lil problems and the odd issues that need to be sorted. However, the love comes from the sense of accomplishment when we finally solve an old glitch and restore it to proper working order.

                        Now get back in the game and fix those power locks!!!
                        E30 M3 / E46 M3 / E83 X3

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                        • #13
                          Originally posted by ///Empowered
                          Now get back in the game and fix those power locks!!!
                          already did that! well sorta. i installed an el-cheapo keyless entry instead of fixing the sticky door cylinder. i'll do that sometime else


                          however once i got my car on the lift and started checking all my bolts as part of a track inspection, i discovered someone replaced my two lower diff bolts with those of the wrong thread pitch and with 18mm heads :grr: chased the threads and put in the proper bolts and they torqued down properly
                          James
                          sigpic

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