BMW R1200RT/R1250RT Forum

NOTE: Before anyone responds, I think I've sussed out the problem. I'll update you if I'm correct, but it seems that the ABS/Speedo sensor ring is the problem, in that the 2005 has 100 teeth to the 48 for the 2009.  Haynes tells me that I'll have to plug it into a "tester" after I've swapped them to stop the warning lights.  Anyone know what this entails and if only a BMW dealer can do it?  I'm also assuming that, even if the lights are on, that the ABS will be functioning properly? My original post follows:


Swapped out a damaged front wheel with one from a 2005, now the speedo is dead and the "brake failure" light is on constantly, even tho' the brakes seem fine.  The Haynes warns of damaging the ABS sensor on the left fork (which doesn't appear damaged or displaced) when removing the wheel but I'm guessing it does double duty with the speedo sensing?  Anybody know if the sensor wire goes directly to the central electronics unit, or if there is an intermediate connector I can use to replace the sensor wire without disassembling half the bike?  On a separate subject, is it possible to re-form a slightly deformed front rim?  I know aluminum is hard to work with.  I swapped the wheel out of fear it might come off the bead while riding, but it apparently costs $1000 (!!!!) for a new one.

This thread may be helpful, "Speedo Failure" viewtopic.php?t=9

On your RT the wheel sensors connect to a harness that directs the signals from the speed sensors to the ABS controller:


In the diagram above the front and rear wheel speed sensors (B9193 and B9194 respectively) at the bottom of the diagram run their signals to a harness (via connectors X9193/9194) that ends at the ABS computer (A9190).

The wheel sensors are used in several systems; speed sensing for speedometer/odometer, ABS and ASC (traction control, if fitted).

It is also advisable to read (and try clearing) fault codes using a GS-911 or MotoScan setup; this may give you more insight.



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After reading that the sensor rings had a different number of slots (teeth), I did some research...indeed the earlier RTs (up to Aug 2006) use a different one:



I have both an early ‘06, and an ‘09 sitting here:
2006 RT:


2009 RT:


You could consider replacing the front sensor ring with one appropriate for your 2009 bike, which is readily available (both new and used thru a variety of sources). Since I believe you recently replaced the front wheel with one off a 2005 model, perhaps you could migrate the correct sensor ring off your old front wheel to your current wheel.

Detail on swapping out rotors/sensor rings:

https://shop.maxbmw.com/fiche/NotesPart ... 9543_1.pdf

BTW...here’s an explanation on how I-ABS II works in the 09 R1200RT...read the section titled “sensors”:

http://largiader.com/abs/abs2.html

This implies the processors compare the wheel speeds...it COULD be that with nearly twice the frequency of that signal coming from the front wheel (with that ‘05 sensor ring on the front) your ABS computer thinks something is wrong, hence the warning light.

A GS-911 scan might yield an error of “Front (or Rear) Wheel Speed Sensor: Signal Implausible”; this error can also be generated by a bad, misaligned or disconnected sensor.

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UPDATE:

It appears (at least with some BMW bikes) the GS-911 can read speed from the sensor...and calculated speed from the page “Input Data”:



I’m curious about this, so as time permits over the next couple of days I’ll hook my GS-911 up to my 2009 RT and see if this works.


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I had a few minutes so I hooked up the GS-911 and my laptop to the RT.

I navigated to the ABS module in the GS-911 software; from that menu I can get to real-time data for the front and rear wheel speeds.

As opposed to some other models of BMW bikes it does not show “calculated speed” but that’s really not a concern because we are testing individual speed sensors.

Note: I tested again, this time with the MotoScan Ultimate app on my Android phone and the Bluetooth OBD2 reader... it also reads front & rear wheel speeds.


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First, thanks for all your effort and input.  Second:  Success!  All warning lights are now off, without "plugging in a testing unit" as Haynes said.  Please note, however, that the brake rotors of the 2005 and 2009 RT are not interchangeable.  The 2005's bolts have a wide collar that fits into a wide hole in the disc rotor.  This doesn't affect the  "speed ring" that I swapped out.  Thanks again.

Great!
So the speed ring made the warning lights go away...but is your speedometer still inoperative?


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Thanks, Rangemaster.  Yep, speedo's working.  Now I've got no excuse for speeding - "Check it out, Officer:  my speedo died!!".

Wow...your speedo quit working and the only thing wrong was a front sensor ring.

Usually with a failed speedo it’s the rear sensor system... but this might be a “undocumented feature” in certain failure modes that not only lights up the ABS warning, but kills the speedo.

I’m going to try a few experiments on my 2009 RT... it would be easy to pull the sensor off the front and see if that fails the speedo.


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R-master,  The ring wasn't faulty, it was just the wrong ring for the 2009 unit (on the 2005 wheel I swapped onto the '09) in that it had a diffferent number of "teeth" that the sensor was counting to calculate the speed.  Don't know what you would learn from messing with your sensor, and why court disaster?  I'm just glad I didn't have to pay someone to kill the warning lights!

jackronner wrote: R-master,  The ring wasn't faulty, it was just the wrong ring for the 2009 unit (on the 2005 wheel I swapped onto the '09) in that it had a diffferent number of "teeth" that the sensor was counting to calculate the speed.  Don't know what you would learn from messing with your sensor, and why court disaster?  I'm just glad I didn't have to pay someone to kill the warning lights!

I understand that, but occasionally we get RT owners with inoperative speedometers.

It’s typically the rear sensor that causes this as that’s the primary input to the speedo; what has me curious is an inaccurate front sensor signal gave you an ABS warning (and I know why now) AND a dead speedometer.

By doing some additional limited testing with the front sensor removed (as in unbolted and wire-tied safely out of the way) it might replicate the problem.

The speed sensor isn’t a proximity switch (which has two states of output...off and on), but a device what has an analog output in the form of a sinusoidal waveform that varies as the slots in the ring pass by the sensor.

I don’t mind doing this...I’m an electrical engineer and deal with sensor systems and love a puzzle. I have the test equipment and it’s been raining nonstop here for days!

It’ll be a nice ‘science-fair’ project, and helps me better understand my bike.


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Well, you didn't tell me it was raining!!  Of course you need something to do!  I'd say good luck, but it doesn't sound as if you need it.