Help - front brake pressure too high - RED WARNING flashing BRAKE FAILURE

[turtleossie]

I'm going out later to wiggle connectors and clean the rear wheel ABS pick up etc - I don't hold much hope regards the rear sensor but will stand to be corrected.

I don't see how - according to the post copied earlier - rear final drive causes the rear servo to stick on? I also agree with the post that there is no rear brake pressure being applied while the servo is stuck on. When pressure is applied to the rear pedal the servo acts as it should i.e. finds it's position and then SHUTS off - only to come back on again when the pedal is released.

As the bike initializes I do get a small whiz of the servos, they then turn off, then the RED triangle and flashing brake warning (which usually goes off when you ride for a little bit) both come on. So the bike thinks there is a fault with the ABS [according to the manual] ... and has gone into fault mode BEFORE I have even started the engine and moved away...

In this mode - when you move off BOTH the triangle (solid ON) and brake warning (flashing ~4Hz) remain on/flashing. Sometimes you have servo assisted brakes .. and sometimes you don't - which is a bit scary.

In the mode - just turned on ignition and have not started the engine - I don't have any front brake servo until I hit the rear pedal, at which point the rear servo sticks on, but I then get front servo going on and off as usual when the lever is pulled/released.

I've studied the Haynes manual cct diagram and will trace the rear brake light all the way to the ABS modulator (and front for that matter) with a DVM to see if there is a break in the line AFTER the in-line connector behind the battery. Other than that I see nothing (other than the ABS modulator) that could cause this problem.

This final drive fixing my issue, according to PIEBAPS, is a mystery. What in the final drive could cause this problem? i.e. what signal is it sending and where? I get final drive when the bike is moving .. but I'm not moving .. unless of course the sensor is so gunked up it is sending nothing ... then I can see bad things happening.

Now I'm thinking about this I suppose the bike could be really clever .... imagine the speedo reads zero but the ABS pick-up is covered in gunk and is thus reading as if the wheel is spinning ... the bike works this out and is turning on the servo to try and stop the bike .. whic isn't moving ... HO HO HO .. now I'm dreaming

I intend buying a GS-911 as soon as I can afford - which will be a long time if I end up having to replace the ABS modulator.

I'll keep updated - meanwhile any bright ideas greatly appreciated. A local GS-911 would be a godsend. South Wales area.

 

[littleredrooster]

....As the bike initializes I do get a small whiz of the servos, they then turn off, then the RED triangle and flashing brake warning (which usually goes off when you ride for a little bit) both come on. So the bike thinks there is a fault with the ABS [according to the manual] ... and has gone into fault mode BEFORE I have even started the engine and moved away...

No! The final part of the initialisation process isn't completed until the bike moves forward at about 5mph.

 

[turtleossie]

But it's failing the initialisation routine BEFORE it gets to that that step [moving forward and checking wheel movement].

Thus the RED TRIANGLE lights up = ABS fault.

I agree the red text is flashing as well, and does normally go off after a few roatations of the wheel - in this case it doesn't. Both triangle and flashing text remain on ... all the time, moving or not!

Questions is what device is failing during the ABS / brake check initialisation routine....

 

[Pukmeister]

The wiring diagram shows the bikes ABS unit has external inputs such as front/rear wheel speed and front/rear reservoir internal fluid level. I don't know about internal inputs for brake line pressure, although the bike is reporting high brake pressure in the front circuit therefore it suggests the ABS unit computer monitors internal brake pressure rather than just modulating the pressure by mechanical means.

I am beginning to think your ABS unit may have a fault with a transducer input, the most probably cause is that it is seeing a fault with a wheel speed sensor (rear as suspected) or fluid level sensor input hence the red triangle staying on after initialising.

I can't remember exactly if the red triangle should go out after self-test on the earlier ABS, leaving the brake failure warning flashing on its own until 5mph (my current 2008 bike has the later ABS so works differently) but I think thats how it should work. Anyone with an earlier 1200GS care to comment ??

The rear wheel speed sensor inside the final drive is just a simple inductive sensor, which will give a square-wave output to both the speedo display and ABS unit at a frequency proportional to wheel speed. The crownwheel inside the final drive has steps machined into the rear face and as they rotate past the sensor, this generates the square-wave output as the metal 'lands' pass through the magnetic field of the inductive sensor, cutting lines of flux and generating a waveform.

Because the sensor is slightly magnetic, it attracts any microscopic swarf and wear particles from the oil thrown over it until it ends up with a tiny xmas tree of swarf growing off it. This reduces the ampitude of the square-wave signal and may prevent it altogether. I suspect the speedo is pretty rudimentary in converting a square wave into a needle movement on a dial, wheres the ABS is probably more complicated and sensitve to the size and frequency of the signal produced.

What I'm trying to say is that just because your speedo is still working, doesn't mean the sensor could not be affecting the ABS. For the sake of a half-hours effort its worth giving it a quick clean, replace and test ride.

EDIT: Turtleossie, as a forum newbie you may not realise that to PM forum members you need to subscribe, at £12 a year. Although not mandatory to subscribe, it would help if you could receive PM's from people so this thread doesn't become a hundred pages long.

 

[turtleossie]

Hi - normal op would be Red triangle > then yellow > then triangle off > with brake failure text flashing till the bike has moved ~5M. Then text goes off.

I get red triangle > yellow triangle > back to red and the text flashing. Nether go off if I move the bike..

I've taken the tank off again - re-checked everything and also the pick-up sensors on both wheels.

Nothing doing.

If they do tell me tomorrow it's the modulator I think I'll just transform the bike to non-ABS / non-servo assisted. How much less complicated [and expensive] that will be... Motoworks tell me the bits cost about £50 .. it certainly seems easy enough. There's nice link in points at the headstock and behind the right ankle plate. Worst headache is getting rid of the red triangle warning, apparently BMW refuse to re-program.... I'll need to read if I go this route.

Not looking forward to tomorrow and the bad news...

 

[Pukmeister]

Worst headache is getting rid of the red triangle warning, apparently BMW refuse to re-program.... I'll need to read if I go this route.

Not looking forward to tomorrow and the bad news...

From the ADVrider site:



http://advrider.com/forums/showpost.php?p=7948825&postcount=16

EDIT: I would also consider fitting a replacement battery unless you are 110% positive that your battery is holding a full charge (open circuit terminal voltage above 12.7vdc, preferrably slightly more)

 

[turtleossie]

New battery fitted last Wednesday ... one of the first things I tried. Thanks for pointing out the obvious thorugh, easy to miss.

 

[Demongroover]

C'mon, what's happening, suspense is killing me! ....

 

[turtleossie]

So went to the BMW main dealer this afternoon - having been to an independent last week.

Same story - ABS modulator has gone, front servo isn't working, rear one is sticking on.

£1375 for the modulator plus ~2HRS labor to sort out. Said they can probably do it for £1500... They can even rent me a bike for £15/day while they do it! I tried not to laugh.

Work comes with a two year warranty - so I suppose that is something.

Anyway, I either bite the bullet - or transform into a non-servo/ABS system.

Frankly - having ridden to the dealer and back with no servos I'm thinking I like the servo assist. The one time I need ABS I'll be glad of that too!

I can always sell after two years, then I'm guaranteed not to have another big bill ... for this anyway.

I'm going to drink some beer and have a think - your thoughts appreciated.

Suffice to say - today was not a good day

 

[Pukmeister]

Another possible option worth investigating is repair by a car ABS specialist if such a service is available. Perhaps an automotive specialist could sort it for less money??

Someone like this might be worth a phone call:


http://www.autotekelectronics.com/newautotek/UK/index.php

 

[turtleossie]

So hopefully to the end of this story....

Today I phoned BMW UK customer services and gave them a bit of what for regards the whole servo/ABS situation. They sugested I speak to the dealer who can put in a request for some 'financial assistance'.

I phoned my local dealer who could not have been more unhelpful if they tried. I suppose I have already given them £58 for confirming the fault - I ended up putting the phone down on them. To busy to fill in an on-line form that takes < a min.......

Then I 'cold call' another fairly local MOTORADD dealer and bleat out my story - this time the guy I spoke to could not be more helpful. Went out of his way to sort the issue out, all done an dusted 30 mins after I initially called him!

Bottom line is that in a week or so I will be taking the GS to his shop for fitment of a brand new ABS modulator.

BMW will pay for parts, I will pay for labour and brake fluid.

I recon that's saved me £1375 then ......

Next time the unit fails I'lll be ready with looms/lines etc to just get rid of it. I'm happy I should have another few years of ABS and servo assist.

Thanks to all for your help.

Hopefully .... THE END

 

[61nearlybold]

Name and shame the first dealer.
Name and praise the second dealer.
It may help the next person who has a similar problem as its obviously not a home fix. A very interesting link with a happy ending.

 

[Demongroover]

Indeed, who is this helpful dealer?

And I'm glad they finally decided to help out and resolve the issue.

 

[turtleossie]

I'll name and shame once the work is done and dusted ;-)

I'm thinking of buying one of these GS-911 diagnostic tools, what are peoples thoughts on this? Worth the money ...... ?

 

[Pukmeister]

I'm thinking of buying one of these GS-911 diagnostic tools, what are peoples thoughts on this? Worth the money ...... ?

Yes and no.

I've had a 1200 in one guise or another since they first came out, and have mates that own them so my investment was worth it. I bought mine as part of a group buy arranged by 'Slowdown' on this forum (thanks again Neil).

If you don't do home servicing, or aren't going to own your GS/GSA long term (or other models supported by GS911) then they won't be worth the investment.

IIRC I paid about £300 for mine, but I did my own servicing so its probably paid for itself by now and is going to save me in the future once my GSA is out of warranty and thus serviced by me.

 

[turtleossie]

One of the questions I was asked to qualify for 'financial assistance' from BMW was "does the bike have dealer service history?"

I get the feeling if I had said no then BMW would also have said no. Service yourself, then you look after yourself kind of thing. I suppose in a way that would be fair comment.

Thank God the previous owners have ensured the BMW stamps are up to date.

The local independant BMW guy (not the dealer who was as helpful as a cow pat) said a routine service would cost £150 with BMW parts fitted. Wonder how that translates to an actual MOTORADD dealer. Are they much more expensive ....

The independant close to me used to work for BMW, so knows what he's doing - and nor is he a cow pat!

I'm more than used to servicing my bikes myself but in the case of the GS I think I'll keep it topped up with Beemer stamps.

 

[turtleossie]

All done - brakes are better than ever

10/10 Bristol Motoradd - Bath Road

0/10 Riders of Cardiff

 

[61nearlybold]

Agree with your rating of Bristol BMW but they are loosing the franchise because they will not commit to a masive investment (same as BVM last year

 

[parabiker]

Arse,

my 2006 has done exactly the same today. Solid red traingle. Reset on ignition but then followed by ABS light flashing fast and no servo assist at all.

Any chance you could let me know the part number for the replacement?

Simon

 

[turtleossie]

HI

I don't have the part number dude - it's a BMW part and they don't give out the numbers ....

Have you checked all the easy stuff? Leaver stuck in/on, is the rear brake light on all the time maybe?? Out of interest do you get a servo when you press the rear brake? Does it go off when you release the pedal? Whats the failure mode - total or partial?

Worth trying to fix - a new modulator is £1450 plus fitting - unless you get very lucky!

Other option is to remove - Motoworks do a kit for ~£80 - although I'm not sure where this leaves insurance cover. Something I was going to ask, I suppose you don't have to own up, but if they ever find out you've messed with the ABS unit that's sure to be bye bye payout.

Real shame about the Bristol BMW crowd - first time I met them - thoroughly helpful bunch of people. They sure saved me a grand and a half