R1200 GS final drive ABS sensor

[tuckerqvmcc]

Ok to cut a long story short my May 2004 R1200 GS Final Drive chewed itself to pieces after 20,450 miles....no warranty left & no BMW good will (worth considering) given.
Bought an '08 FD unit with drain plug c/w ABS wiring off ebay, drained the oil from it, removed the ABS sensor to syringe new EP oil & fitted it....perfect, but ain't got speedo now & brake failure light staying on.
Does the can bus system only recognise the old ABS wiring harness of my original '04 unit by any chance?
Any idea's, gotta be something simple surely....'08 ABS loom looks fine, no breaks or damaged connections etc.
Thought I'd maybe plugged the loom in the wrong way round under the tool kit tray but it only fits on one way?

 

[Pukmeister]

I believe the ABS sensor inductively counts the teeth on the crownwheel, which would suggest that the new ABS sensor isn't working, or isn't feeding a signal to the speedo and ABS computer (assuming the rear wheel is turning). Can't you just fit your old ABS sensor and see what happens?

The only definitive test of the ABS sensor would be to look for a square wave output with an oscilloscope as the rear wheel spins (not easy or safe to test whilst on the centrestand).

Last time I worked on my 1200FD I just unclipped the ABS sensor wiring and moved it out of the way, I didn't disconnect it. It is possible you may have a poor termination in the loom after disturbing it ?

 

[tuckerqvmcc]

Tried to change the new 2008 sensor over to the old 2004 one but the 2008ABS unit that fits into the FD at back wheel is slightly larger than the 2004 one doh!
The 2008 ABS sensor has a metal washer and rubber O ring on it also to seal the joint.....(2 different sized ABS sensors 2004 + 2008) but same connector under tool kit bag.
Just wondering if on board computer needs reset by BMW dealer because it was removed while renewing EP oil or because it's a 2004 computer on bike trying to read a new 2008 ABS sensor?
Clutching at straws here folks?

 

[wilbjr21]

If it's any help the number of front sensor ring teeth decreased with the introduction of the Continental Teves ABS system (non servo): so the rear ABS ring will probably be different ........... sorry.

 

[pinkytiff]

I had exactly the same symptoms - i.e. no speedo & brake failure light stayin on, when I put an ABS ring with the incorrect number of holes on my 07 GS12. Logic then says its gotta be something to do with that ring.........

 

[RickG]

If the sensor is very cunning and talks to the computer via the can-bus rather than sending just pulses down the wire, it could have a different address than was used in the old system in which case the computer won't be able to talk to it. That's speculation, I've no idea for sure. Or it's simply knackered! Do you get the same fault with the old sensor plugged into the loom (even if not poked into the FD)? It might provide more clues as to what's wrong

 

[tuckerqvmcc]

Before removing my wrecked 2004 FD complete with sensor & loom, the ABS sensor & speedo worked perfectly....
I assumed fitting a 2008 FD with its own ABS sensor & loom straight on would just connect straight into the main loom under the BMW tool kit (which it did) with same connector 1&2 pin connector.
Now that means the issue can't be counting teeth surely as the correct sensor is fitted to the approriate 2008 FD; so I'm assuming the 2004 on board computer ain't kitted out to read the new 2008 ABS sensor or loom?
I drove the bike for about 20 miles that evening to test out the newly fitted 2008 FD (into work & back) & that's when I discovered the brake failure light and speedo not working.
My predicament now is do I carry on riding the bike til I get in touch with local BMW dealership or am I putting myself in a position of danger (possible ABS failure) cause I've heard all sorts of stories about ABS failing on the GS with back wheels overheating & locking up?
I am also aware that the gearing/drive ratio's etc are completely different on the 2008 FD compared to my 2004 model.....
Any info appreciated folks?
Gonna have to get it sorted one way or the other.....

 

[wilbjr21]

Before removing my wrecked 2004 FD complete with sensor & loom, the ABS sensor & speedo worked perfectly....
I assumed fitting a 2008 FD with its own ABS sensor & loom straight on would just connect straight into the main loom under the BMW tool kit (which it did) with same connector 1&2 pin connector.
Now that means the issue can't be counting teeth surely as the correct sensor is fitted to the approriate 2008 FD; so I'm assuming the 2004 on board computer ain't kitted out to read the new 2008 ABS sensor or loom?
I drove the bike for about 20 miles that evening to test out the newly fitted 2008 FD (into work & back) & that's when I discovered the brake failure light and speedo not working.
My predicament now is do I carry on riding the bike til I get in touch with local BMW dealership or am I putting myself in a position of danger (possible ABS failure) cause I've heard all sorts of stories about ABS failing on the GS with back wheels overheating & locking up?
I am also aware that the gearing/drive ratio's etc are completely different on the 2008 FD compared to my 2004 model.....
Any info appreciated folks?
Gonna have to get it sorted one way or the other.....

Assumption can be a problem here. It's a different braking system so the number of pulses, ie. the ring, may differ.

 

[tuckerqvmcc]

Well after a quick chat with a friend at my local BMW dealership it looks like the gap (ring) may be the cause of my problem but won't know until they put it through the computer.
I ain't changed anything as far as ring/gap on the sensor is concerned other than taking it off to refill the FD with new oil, it was just a straight forward swap of FD's. Apparently the gap is so sensitive that a movement of even a few thou of a mil will knock it outta sync!
As for riding the vehicle there is no question of any long term damage without speedo or ABS working as the brakes will just be a little sharper but can compensate for that with ease of hand.
So up to my local dealership on Monday for a quick on the spot check of the sensor gap and hopefully up n running again!
Thanx for all the feedback folks, hope this info is of use for future reference?