Gurus...Does anybody out there know that if the speedo sensor pickup wire gets graunched / cut and the rear ABS sensor is still intact and you're still traveling at speed, does the ABS alarm come up on the dash board? In other words, is there any interaction between the speedo sensor and the ABS sensor in the ABS computer/electronic wizardry? Does the ABS computer have an I/P from the speedo sensor?

I imagine that there is, inasmuch as if the speedo is indicating that the wheel is still rotating and the ABS sensor indicates that the wheel has stopped rotating, thus reducing the brake pressure allowing the wheel to rotate again, before applying full pressure again, in that loop. But if the speedo I/P indicates that the wheel has stopped rotating, but the ABS indicates that the wheel is still rotating, with no brake applied, it should generate a fault.

This is pure supposition on my behalf. Any info in this matter would be greatly appreciated.

Rickmeister.

AFAIK the speedo sensor has no input to the ABS.
The ABS is a stand alone thing and gets all info regarding vehicle speed from the front and rear sensors.

Rick you could try to read the front sampler to see what info is being fed to the abs unit, that way you could disern what the back should be doing, and in doing so determine if its ok to ride with the wires open or if you require a sampler at the rear to settle things, one presumes that if the sampler at the rear is active then it needs to read rotation, if there is none then you have an issue and fault codes appearing relative to the front,sound fair?

Ulrich_Grabau wrote:Gurus...Does anybody out there know that if the speedo sensor pickup wire gets graunched / cut and the rear ABS sensor is still intact and you're still traveling at speed, does the ABS alarm come up on the dash board? In other words, is there any interaction between the speedo sensor and the ABS sensor in the ABS computer/electronic wizardry? Does the ABS computer have an I/P from the speedo sensor?

I imagine that there is, inasmuch as if the speedo is indicating that the wheel is still rotating and the ABS sensor indicates that the wheel has stopped rotating, thus reducing the brake pressure allowing the wheel to rotate again, before applying full pressure again, in that loop. But if the speedo I/P indicates that the wheel has stopped rotating, but the ABS indicates that the wheel is still rotating, with no brake applied, it should generate a fault.

This is pure supposition on my behalf. Any info in this matter would be greatly appreciated.

Rickmeister.

For futher confirmation of my answer the answer I have now is "there is no interaction between speedo pulsing and ABS input"
The ABS system is a stand alone system and will work properly if the speedo and sensor are chucked in the rubbish.
It reads front and rear wheel speed relative to each other and rate of deceleration, so that if you lock both wheels instantainiously then it can read that the rate of deceleration is far too rapid for normal brake use and releases the pressure and allows the wheels to turn again. The ABS reads 200 pulses per revolution of each wheel where as the speedo only reads 12 per revolution which would not interact well at all as a third sensor even if it was used.

Rick I presume that since the bolt broke and the speed sensor wire was damaged the ABS has been acting up or just simply not working. The best info you can get for that problem is from the guru of K ABS Tosi Tabuki here http://bmwk10075abs1fix.web.fc2.com/ Check it out using his instructions and you cant go wrong and if you need a repaired ABS 1.5 unit I have one here that Tosi repaired 3 months ago and has a warranty on it from him. I would sell for what it cost me plus postage and exchange of the non working one.
If anything I reckon that yours may just need a reset.

+1 That there is no interoperation between the speedo and ABS... and thats with a double check of Tosi Tabuki's website which show the connections made to the ABS controller...

Thanx, Lads! After I posted the original question, I remembered Tosi's screed, and looked it up. V. informative!!

Bought replacement speedo sensor from Steve. Stud replaced by a new found friend who does these things. (managed to weld a nut on top of the broken stud and unscrewed it that way.) When I removed the seat and went to remove the ABS computer from the rear duck-tail, the computer literally fell into my hand! The plug somehow came adrift!

Anyway, off to THE SHED and to start the re-assemble.

Thanks again!

Rickmeister.

Sounding and looking much better...Rick.