Brake warning lights flashing

[opposedtwin]

This topic has been analyzed adnauseum........almost. And I have researched all or at least a lot of them before submitting this so here goes as briefly as possible. My brake warning lights started flashing so I changed brake fluid and made sure all levels were correct. Still flashing. Replaced battery. Still flashing. Switching on ignition activates servo and front brakes perform as they should but rear brakes barely work and there is no servo noise when depressing rear brake lever. Brake light comes on using front or rear levers. Take bike to BMW dealer for a diagnostic check and was told that when they connected to the plug on my bike they could not get a code to point them to what the problem(s) could be. Still charged me a $100 and lights still flashing. Got home pulled the seat off and noticed that each time the ABS failure blinked there was a very low clicking noise and it was coming from an ABS relay in the fuse box. There are two identical blue relays and the inboard relay was the one clicking. When the brake lever was depressed the clicking noise would speed up to twice as fast, similar to the noise a turn signal flasher makes when a bulb is burned out. Switched the relays but it made no difference. Removed the inboard relay and clicking noise stops and flashing lights stop flashing but the smaller left light with the triangle is still on. Rode the bike and everything works the same as with two relays. Front brakes function normal but still no servo for rear brakes. At least I eliminated the annoying flashing light! Questions: Could both relays have gone bad? What exactly is the function of those relays? Buy two new relays? Could a bad rear ABS sensor cause the servo not to actuate? Suggestions? Going back to my BMW dealer isn't a viable option.

[sweatmark]

The relay (K9197) you removed functions only to control the iABS brake failure/warning lamp. The iABS controller switches the relay coil on & off, which in turn toggles power to the lamp. As you've discovered, pulling the relay prevents the ABS lamp flashing, but does not correct whatever iABS fault triggered the lamp in the first place... Hence the continued lack of rear brake servo.

The other blue relay has nothing to do with iABS.

While I've never seen actual iABS1 documentation explaining the controller fault logic, my guess is that rear ABS wheel sensor has a problem. Your troubleshooting points to that possible fault, or else the rear brake servo is FUBAR. I would check the rear ABS timing ring/tone wheel to see if it's damaged, and pull the sensor out to clean the "business end" of any dirt or metallic debris that might be attracted by the sensor's bias magnet. Also check the sensor's wire run along the swingarm and up the subframe, to connector on RHS under seat.

No, your relays appear to be fine. Don't replace them.

The rightmost relay is power relief 2, assuming your bike is a 2004+.

[opposedtwin]

Thanks for your reply. FWIW my bike is a 2002 model. Pulled he rear sensor and cleaned it but problem remains. Have located a used one off the same model as mine and will buy it to see if that is the cure. Would prefer to switch to manual brakes if this doesn't work but dealing with the electrics involving speedo and rear brake light is over my head.

[sweatmark]

For the R1150R Roadster, switching to non-ABS brakes is simple, and your speedometer operation is not involved because it is driven by the drive & cable at front wheel. The same project for the Rockster is more complicated, because its speedometer requires an electronic pulse signal created by the iABS controller.

Hope the rear sensor swap works for you. If not, the conversion is really easy.

[opposedtwin]

Thanks for your help sweatmark. Rear sensor on order. You said switching to non ABS on my Roadster was simpler than on the Rockster. Do you have a link for the Roadster switch to non ABS?