ABS Warning Light - on solid - K-Bikes.com - Excellence in Motion
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post #1 of 5 (permalink) Old Nov 3rd, 2016, 11:56 pm Thread Starter
Join Date: Sep 2016
Location: San Jose, CA, USA
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ABS Warning Light - on solid

Recently picked up a 2008 K1200S with $30K miles. Love the bike but it is having the pesky brake failure light problem. When I turn the key on sometimes the ABS warning light comes up flashing and turns off as I drive away, and sometimes the warning light comes up solid "on", and does not turn off while I am riding. After the bike sites for a few hours or a day or two, it is a 50/50 chance if the warning light will come on flashing or solid "on".

1) Since when the ABS light comes on flashing and goes off as I ride away, I am assuming the ABS sensors (front and rear) are working OK. I did check the clearance on the front wheel between the sensor and the ABS sensor ring on the wheel @ 20 thousands.
2) I inspected the wires to both of the ABS sensors for any nicks in the attach system.
3) I don't see any wires or sensors associated with the brake shoes, but replaced them anyway because it was time.
4) I also bled the brakes and made sure the brake fluid containers were filled properly. Also I don't see any sensors associated with brake fluid levels.
5) The battery is almost new. It tends to hold its voltage around 12.2 - 12.4 volts.
6) Soooo....does that leave the ABS Brake Servo Control Unit? I do not understand the function of this device. I understand the valve body will distribute braking power to both the front and rear wheels, but when is the servo (motor) turning? I can't hear it running. I have a garage stethoscope but can't really hear anything going on in the servo. Does it spin whenever the key is on? Does it spin only in an ABS braking situation? I know they are expensive and I can disassemble to check the brushes on the motor, but I'd like to know there is a good chance that that is my problem before i rip into it.

Any counsel from someone with experience would be most appreciated.
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post #2 of 5 (permalink) Old Dec 24th, 2016, 3:34 am
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Location: Albury, NSW, Australia
Posts: 61

Look for forums about bleeding your brakes.
Your brake reservoirs are used to pass pressure to the control unit. You need to bleed the brake circuit to the control unit as well as the brake circuit to the callipers.
You might have a minor problem or you might have a big problem.
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post #3 of 5 (permalink) Old Dec 30th, 2016, 7:53 pm
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GS911 can detect the fault code. Might be a faulty ABS sensor.
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post #4 of 5 (permalink) Old Mar 14th, 2017, 1:06 pm
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don't know if you are still having an issue, but you might find these guys helpful: https://modulemaster.com/rebuilds/sh.../abs-ate-abs4/
I am very new to BMW KS 2008 and can not tell you anything about this company other than the address and they are much cheaper than BMW. Good luck.

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post #5 of 5 (permalink) Old Apr 17th, 2017, 10:03 am
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Location: Seattle, WA, USA
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There are like 3 bleed nipples on that damn module under your seat. I just have a Bare Bones ABS on my 08 K 12 S and like it that way but I have helped people with the full Servo Assist systems. You should do a complete fluid replacement/bleed. It's probably never been done and the bike is what, 8 years old now. What's going to run out into the jar is going to scare you. %^)

Even if you don't see a wire running to some particular point doesn't mean the system doesn't know what it's status is. On a very long trip 2 years ago my rear pads where getting thin and my system figured it out and flashed the ABS light on my display. The only wire back there is to my wheel sensor. The system must be able to determine what the status of the pads were via the fluid movement thru the main module.

The Servo Assist ABS system is just about the most touchy mechanism on these bikes. Very often even after you do your best shot at maintenance and repair, you still have to drag it into the dealership to get the warning light to go out. It ran the last guy I saw about $300. They said he did still have air in the module and a valve in the module was sticking.
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