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Thread: 1992 K75S ABS computer computer testing

  1. #1
    broadstone
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    1992 K75S ABS computer testing

    I tried determining ABS fault codes using a digital voltmeter which was difficult to read and I was getting fault code 6 which would indicate a problem with the ABS relay. To confirm, I used the LED test circuit method and that pretty clearly indicated code 7 which implicates the ABS computer. Yes, my battery was at a high charge of 12.8V. I could buy a replacement brain but I have questions that I need answered before I make a commitment to spend even more significant money on this bike.

    My question, then, is whether the test,as written, is the final word on the diagnosis of a bad computer? Can I assume that because the blipping lamp goes all the way to 7 and stays on there, that 7 is the only code that will be displayed and that's the final word? If it stopped at 7 does that mean that it simply did not make it to code 8 and that could be bad also? Also just because it made it to 7 and stops does that mean that 1 through 6 are definitely OK?

    I know this is kind of a convoluted question but the purchase of a computer is expensive so any suggestions will be appreciated. BTW, when I thought the fault code was 6 I bought a used relay but haven't installed it.
    Last edited by broadstone; 11-17-2012 at 12:19 AM. Reason: 1992 mis-titled thread

  2. #2
    A bozo on the bus deilenberger's Avatar
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    Quote Originally Posted by broadstone View Post
    I tried determining ABS fault codes using a digital voltmeter which was difficult to read and I was getting fault code 6 which would indicate a problem with the ABS relay. To confirm, I used the LED test circuit method and that pretty clearly indicated code 7 which implicates the ABS computer. Yes, my battery was at a high charge of 12.8V. I could buy a replacement brain but I have questions that I need answered before I make a commitment to spend even more significant money on this bike.

    My question, then, is whether the test,as written, is the final word on the diagnosis of a bad computer? Can I assume that because the blipping lamp goes all the way to 7 and stays on there, that 7 is the only code that will be displayed and that's the final word? If it stopped at 7 does that mean that it simply did not make it to code 8 and that could be bad also? Also just because it made it to 7 and stops does that mean that 1 through 6 are definitely OK?

    I know this is kind of a convoluted question but the purchase of a computer is expensive so any suggestions will be appreciated. BTW, when I thought the fault code was 6 I bought a used relay but haven't installed it.
    The LED test will indicate multiple faults - it can flash 6 times, then a gap in time, then 7 times, or whatever. It repeats the cycle if there are more then a single fault.

    Before you spend $$$ - try doing a long reset of the computer. That means ground the center pin on the connector, turn the ignition on, and hold the ABS button for at least 60 seconds. There are some faults that will not clear with the short reset.

    If you still have the fault after doing that - there is a chap in Japan who is repairing the computers for a reasonable price.. and everything I've heard about his work is positive. Someone will probably have a link or email address for him.. (I don't - but if you're stuck, PM me and I'll ask someone who does have it.)
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders New Sweden BMW Riders
    '07 R1200R (current ride) and some bimmers.. and a Porsche

  3. #3
    broadstone
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    K75S ABS computer testing.

    Thanks. That's very helpful and, based on that explanation I'm comfortable, but not too happy about it, that the computer is the culprit. I've done the reset and have already discussed the issue of brain replacement with Tosi in Japan. He has a trade in policy that helps defray costs and his rebuilt computers come with a one year guarantee . I'll probably still gamble with a used one from a trusted source. Thanks again

  4. #4
    A bozo on the bus deilenberger's Avatar
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    Quote Originally Posted by broadstone View Post
    Thanks. That's very helpful and, based on that explanation I'm comfortable, but not too happy about it, that the computer is the culprit. I've done the reset and have already discussed the issue of brain replacement with Tosi in Japan. He has a trade in policy that helps defray costs and his rebuilt computers come with a one year guarantee . I'll probably still gamble with a used one from a trusted source. Thanks again
    The problem I see with the used one is - the potential for it to exhibit the same failure is high. May be fine now, but down the road? It's my understanding that Tosi also improves what is failing on the ABS brain, making it much less likely to fail (which is why he can offer a warranty.)
    Don Eilenberger http://www.eilenberger.net
    Spring Lk Heights NJ NJ Shore BMW Riders New Sweden BMW Riders
    '07 R1200R (current ride) and some bimmers.. and a Porsche

  5. #5
    BMW uber alles! Zagando's Avatar
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    Jim; I suppose you already discussed this with Toshi but have you checked the ABS brain multi-connector pins for corrosion?

    If there's any chance of a bad connection there it can also show up as a bad brain fault. I would go to the trouble of taking the plug off and inspecting both parts carefully.

    Radio Shack sells a wonderful tool that I would never be without as I do a fair amount of electronic work in my hobby; a fiberglass bristle brush in the shape of a pen that it great at cleaning (actually by scratching or abrading) small connections.

    I do not recall what they call it but it runs around $8 or so and is worth every penny. Comes with an extra set of bristles and is also dandy for cleaning metallic surfaces to be soldered.

    Inasmuch as your bike sat outside and was neglected there is always the chance that your potentially costly problem may be down to a tiny bit of corrosion right in the wrong place!
    ---Jeff

    ex: K75S Berlina R100GS/PD , K100RS , R75/5 , R60/2

  6. #6
    redwombat34
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    Smile long ABS reset

    60 seconds now? Happy to try that. Mine gave up when the battery went dead. Classic reset scenario but it didn't reset after several 20 second tries. I had the beer ready and everything. I know what I'm gonna be thankful for....

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