Speedometer ABS Issue

[mtgill]

Hello all. Over the last few rides on my 2004 R1100S, I've been having ABS brake system failures. The events do appear to be truly random; they can occur occasionally on start up, but are also occurring part way through my ride, or sometimes not at all. Upon braking, I get a 4Hz flash on the ABS warning light and the general warning light. In most cases (city riding), I can clear the error at the next set of lights with key off, then key on. On my last three long rides (out in the country), the problem has cleared on its own. I initially assumed this was some kind of internal self correction, because I'd never actually witnessed the error clear itself; riding along and hear the break servos stop making noise, or look at the display and see that the lights weren't flashing. On my rides today I was able to see the error clear... cruising at 60-70mph, the speedometer dropped to 0mph, the ABS warning light stopped flashing, then the general warning light went out. At the same time, the speedometer came back up to the correct speed. The corrections don't appear to be tied to a loose connection (the roads were very smooth, so no bumps hit to make the connection good/bad), but I wouldn't bet my $ that it's also not the problem. Looking at the wiring diagram indicates a significant number of electrical gadgets that could be the problem...any hints for key components to look at? Bike has 13,000 miles and original battery.

[DrPaul]

Sure it wasn't your tach that dropped to zero rather than the speedometer? Unless your S is different than my RT, the speedo is mechanically driven by the front wheel. There's no 'electrical' connection between it and the ABS system.

[mtgill]

DrPaul, definitely the speedometer.

[Brettendress]

Had a similar problem with my 04 Gs random failure ABS lights. First take the sensor out and clean it but it's probably the ABS sensor. Replaced mine at cost of $135.00 and it corrected the problem. It looks like my old one that failed was hit by something on the road and damaged the cord just a little right by the front wheel and that was enough to make it fail randomly. As for the Speedo problem I don't know how that would tie in? May be two different problems

[ANDYVH]

As far as I know, there is no connection between the speedometer and the ABS system, at all. The ABS system gets all of its wheel speed info and vehicle speed info from signals generated by the wheel speed sensors alone.

Twice in my experience with my ABS equipped R1100RS, the speedometer due to failed cables and failed drive hub (at the front wheel). And in neither case did it impact the ABS system at all, or that it did not generate any ABS system faults.

[AntonLargiader]

The R11S is very unlike other Oilheads. In general you'd probably do better asking tech questions over on the Pelican Parts forum:

http://forums.pelicanparts.com/bmw-r1100s-r1200s-tech-forum/

In your case (Integral ABS) the speedo gets its input from the ABS unit. Sounds like it could be a bad rear wheel speed sensor or a problem in the ABS unit itself. Get the fault codes read.

[mtgill]

Thanks Brettendress, ANDYVH and AntonLargiader for your suggestions. Will check them out.