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Thread: Where are the connectors for the brake wear sensors?

  1. #1
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    Question Where are the connectors for the brake wear sensors?

    I replaced both the front and rear wear sensors when I did my rear pads (the rear had indeed touched the rotor). But the light and "CHECK BRAKE LININGS" message are still there and I cannot get them to reset with any of the known methods (key on, wait 45 sec, etc.)

    I think there may be a corroded connector somewhere in the loop from the E-box to left front to right rear and back to E-box. Are there other splices/connectors inside the car? I really don't want to take the entire interior apart to follow the wire and look for them...

    thanks for any help.
    Charles
    '98 740iL E38 201k, TCG at 190k, 5HP24 at 195k
    '97 540i/6 E39 Dinan blower & stage 1 suspension 114k
    '93 525i E34 "Golf Ball" (hail damaged) 334k

  2. #2
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    Quote Originally Posted by DrCharles View Post
    I replaced both the front and rear wear sensors when I did my rear pads (the rear had indeed touched the rotor). But the light and "CHECK BRAKE LININGS" message are still there and I cannot get them to reset with any of the known methods (key on, wait 45 sec, etc.)

    I think there may be a corroded connector somewhere in the loop from the E-box to left front to right rear and back to E-box. Are there other splices/connectors inside the car? I really don't want to take the entire interior apart to follow the wire and look for them...

    thanks for any help.
    Charles
    ...just to verify...are you turning the ignition to KL R (ignition position 1) or are you turning it to KL 15 (ignition position 2)? It matters...to reset the warning requires that the ignition be turned to position 1 (for 30 seconds). If you're turning past KL R and the ignition is in KL 15...then the light won't reset.

    Become a BMW CCA member! Click HERE to join and feel free to use my BMW CCA member #191509 as a referral.

    2015 650ix GC (Moonstone/Cohiba Brown) <<~>> 2014 X5 50i (Space Gray/Mocha)

  3. #3
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    Yes I am... I have read everything I can find on this warning circuit (including your useful posts) and it still won't reset.

    About three years ago I had a sunroof leak (while away for the summer, of course) and it trickled down the right front A pillar and corroded the passenger airbag sensor and my LKM too! Fortunately I was able to revive the LKM with a careful cleaning of the corrosion with a toothbrush and 91% isopropyl alcohol, distilled water rinse and a gentle bake at 140F. I was wondering if there was a connector for this brake warning circuit in the right front footwell somewhere...
    '98 740iL E38 201k, TCG at 190k, 5HP24 at 195k
    '97 540i/6 E39 Dinan blower & stage 1 suspension 114k
    '93 525i E34 "Golf Ball" (hail damaged) 334k

  4. #4
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    The wires only go to the cluster and thats it. Heres a diagram and a view of the connector. Check for continuity at the pins and at the plug at the wheel. Probably have a broken wire somewhere. Its pin 4 and 20 at the plug behind the cluster. Should be a yellow and yellow/brown wire.
    e38 brake wear sensor diagram.JPGx10114.JPG

  5. #5
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    According to that diagram:
    X118 is the 2-pin connector for the left front pad sensor, and X713 is the 2-pin connector for the right rear pad sensor.
    X10114 is the dash (IKE) connector. So far so good.

    But there are also two (2-pin?)connectors shown, X18145 and X18146. I don't know where they might be. Any ideas?

    I agree a wire is broken somewhere but finding it could be really "fun".
    '98 740iL E38 201k, TCG at 190k, 5HP24 at 195k
    '97 540i/6 E39 Dinan blower & stage 1 suspension 114k
    '93 525i E34 "Golf Ball" (hail damaged) 334k

  6. #6
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    This is one of those oddities of the wiring diagrams. On he WDS, x18145/46 are the connections for each sensor. X118, 713 and 712 (as shown on WDS in place of X713 schematic) are not listed in the individual component info. If you had sunroof leaks in the past, I would pull the passenger seat. I don't know if the circuit loops thru there, but there are many comb splices under there. Even if that's not your issue, if water has been down there you are going to want to clean things up. Have you checked Fuse 18? I don't know if a bad fuse would read as an open circuit causing the warning or if it would prevent it from coming on.


  7. #7
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    Thanks for the info! The connector in the box at the right rear was surrounded by wet mud (I have 2.5 miles of dirt road to get to pavement) and does not look good. It's my prime suspect, but I haven't had a chance to look at it more closely.

    Can you please help me find the part number for the wiring harness connector and pins? The sensor end obviously is new with the wear sensor but I can't find the chassis end. This is the first time in many years that I have actually let brake pads wear enough to hit the sensor. I may just cut it off and install a Weatherpack or similar connector pair...
    '98 740iL E38 201k, TCG at 190k, 5HP24 at 195k
    '97 540i/6 E39 Dinan blower & stage 1 suspension 114k
    '93 525i E34 "Golf Ball" (hail damaged) 334k

  8. #8
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    Ive tried to find this 18146 plug before and had no luck(x377 is your wheel speed sensor). But that was because the wheel caught the wires and ripped them out. I just cut the connectors and connected the wires and taped them really well. That was because i didn't have any connectors at all, you can try to clean them up with some electrical terminal cleaner and some wd-40 and hope for the best.
    Do you have a multimeter? The easiest way to go about this without just guessing is to check continuity between the plug at the cluster and the plug at the wheel well. If there is continuity, something isnt right with the reset procedure. If you dont have continuity, check at the wire itself instead of the plug pins. Pins could be corroded and broken off from the wire.

  9. #9
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    Those connections are not available anywhere that I know of. See this quite often on the speed sensor. I had some from parts cars but got rid of all my parts when I moved a few months ago. Splicing or finding someone parting a car is your best bed.

  10. #10
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    I found the problem, and it's embarrassing especially since I thought I'd checked it. The problem was at the left front sensor - not only is the sensor now worn into the little "bump" on the side, where I can see two stumps of brass loop, it is also worn through where the last mechanic to work on it routed the cable too tight against the caliper! I could have sworn I checked that a few months ago. Oh well.

    Anyway I plugged in a new sensor and turned the key to pos. 1 and waited. Then started the engine - and the blasted light was still on!! Shut the car off again, turned the key to pos. 2 (Ignition on), as everyone says not to because it won't work... waited 30 sec and the light went out and hasn't come back
    '98 740iL E38 201k, TCG at 190k, 5HP24 at 195k
    '97 540i/6 E39 Dinan blower & stage 1 suspension 114k
    '93 525i E34 "Golf Ball" (hail damaged) 334k

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