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An unusual ABS problem


beemerboy

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I experienced an ABS failure this past weekend that has me puzzled. The bike is a 2002 RT with 61K on the clock. I'm the original owner and maintain it by the book. Prior to attending the Un in Wisco, I had Speigler brake lines installed and a complete ABS system flush performed on the bike.

 

The failure occurred just as I was slowing down at an intersection to make a right hand turn. I applied the brakes and immediately noticed two red lights flashing and the near total loss of braking ability. I completed the turn then pulled over and turned off the ignition in hopes that it would reset the system, it didn't so I limped home with very limited braking power.

 

I pulled into my driveway and shut it down then walked into my garage to remove helmet and gloves. At that time I noticed that the bike emitted a servo noise as if the brakes were being applied - this is happening with the ignition key in the "off" position.

 

I pulled the left side panel off and disconnected the battery's negative lead and called my buddy Charlie Coyner ("Biggy" on this forum) to pick his brains about my situation. Saturday night was spent surfing this and other oilhead forums hoping to find if anyone else had encountered the same problem but had no success.

 

Yesterday Charlie came over with his GS911 and laptop but no codes were reported. Has anyone out there heard or experienced the same problem??

 

 

 

 

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Morning beemerboy

 

Need more info-- Were the lights flashing fast or slow & what light was doing what?

 

The servo running with key-off is very strange & not consistent with most I-ABS failures (might be an internal relay stuck)

 

No stored failure codes also points to something not normally monitored by the electronics.

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Morning beemerboy

 

Need more info-- Were the lights flashing fast or slow & what light was doing what?

 

Mornin' DR,

 

The flashing lights were the two red ones located to the right of the neutral light; "ABS" on the top with a triangle containing an exclamation point "!" just below the ABS light. Both flashed rapidly.

 

The servo running with key-off is very strange & not consistent with most I-ABS failures (might be an internal relay stuck)

 

Agreed and that's what has me puzzled. Like most folks here I'm also concerned about the potential cost to fix this issue.

 

 

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Hi Beemerboy, fixing it is easy, you just remove the Servo unit and revert to conventional braking which is great.

What I worry about is if it failed again when you really needed those brakes.

I am sure you have read my distressed observations before about how mine failed a couple of times. I lost confidence in the system and removed it.

However it is too early for that yet, as there is faultfinding that can be done. I am puzzled by the servo chiming in with key off and would be looking for chafed wires.

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Hey Andy,

 

Yes, I recall reading your thread and how you addressed the problem. For the record, I love this bike but I'm also cognizant that it's value must be factored in when considering a potentially expensive repair. Heck, for all I know there's a simple fix..... :rofl:

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Morning beemerboy

 

Need more info-- Were the lights flashing fast or slow & what light was doing what?

 

Mornin' DR,

 

The flashing lights were the two red ones located to the right of the neutral light; "ABS" on the top with a triangle containing an exclamation point "!" just below the ABS light. Both flashed rapidly.

 

Afternoon Beemerboy

 

Were they flashing alternately or together?

 

Also, how much had you used your brakes just before the failure showed up?

 

 

General warning light & the ABS flight lashing alternately at 1Hz is usually a brake fluid level low in the controller (OR) Low-voltage to the ABS controller.

 

Neither above mentioned failures would make the ABS pumps run with key off though.

 

I still can't tell you what is wrong as those servo pumps running after key-off is a very unique failure.

 

Otherwise look for low fluid in controller resivuiours and or a loose alternator belt.

 

You might call Module Masters to see if they can shed any light on the servo pumps running after key-off.

 

 

 

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The lights flashed at the same time. I'd just returned from a rather spirited ride on some twisty mountain roads, about 100 miles total. The fluid level on the handlebar mounted reservoir is as per the book. Battery is just over a year old but I need to check the alternator belt. I'll call Module Masters now....

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The low fluid wrning relates to the reservoir in the ABS controller under the tank. Don't forget your bike has four independant hydraulic circuits - bar to ABS unit, Pedal to ABS unit, ABS servo to front brake and ABS servo to rear brake. There is no fluid connection between any of these.

 

Andy

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Pump(s) running with the key off points directly to an electrical problem, either inside the ABS electronics or in the wiring harness. Before yanking the ABS unit, I'd be hand-over-handing all of the related wiring, after first perusing the wiring diagram to know which wires to look at and to think about where a short could cause the symptoms.

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The lights flashed at the same time. I'd just returned from a rather spirited ride on some twisty mountain roads, about 100 miles total. The fluid level on the handlebar mounted reservoir is as per the book. Battery is just over a year old but I need to check the alternator belt. I'll call Module Masters now....

 

Afternoon beemerboy

 

That thing is REALLY acting weird as there really is no straight forward ABS controller failure that should cause both lights to blink together (REALLY STRANGE).

 

If you rode the heck out of that bike just prior & used the brakes A LOT then it might just be a low voltage issue (known problem with heavily braked I-ABS police bikes)

 

Still doesn't explain the servo pumps running with key off-- You would think that could only be caused by a internal power relay failure)--If it was from an external failure then it would have to be at least 2 separate failures happening together-- somehow the ign 12v into the controller staying alive AND one of the brake switches going open.

 

See what Module Masters tells you.

 

Otherwise maybe try riding the bike again to see if the problem comes back-- if it doesn't then maybe you overtaxed the brake controller (servo pumps ran a lot) & your system went into a low voltage situation.

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....Otherwise maybe try riding the bike again to see if the problem comes back-- if it doesn't then maybe you overtaxed the brake controller (servo pumps ran a lot) & your system went into a low voltage situation.

 

The problem reappears as soon as I connect the battery lead even with the ignition off. As for overtaxing the brake controller.....hmmm, that's an interesting angle. Upon returning to town, I detoured through the Garden of the Gods which at this time of year has lots of slow-n-go traffic. As a previous poster commented, it would seem that there's an electrical problem causing it otherwise how could the system run with the ignition off?

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....Otherwise maybe try riding the bike again to see if the problem comes back-- if it doesn't then maybe you overtaxed the brake controller (servo pumps ran a lot) & your system went into a low voltage situation.

 

The problem reappears as soon as I connect the battery lead even with the ignition off. As for overtaxing the brake controller.....hmmm, that's an interesting angle. Upon returning to town, I detoured through the Garden of the Gods which at this time of year has lots of slow-n-go traffic. As a previous poster commented, it would seem that there's an electrical problem causing it otherwise how could the system run with the ignition off?

 

Afternoon Beemerboy

 

On the servo pumps running (@ key-off) obviously that would have to be an electrical issue, question is, where is it, & IS that the ONLY problem.

 

If internal to controller then possibly an electronic issue causing the power relay to stay energized, or an internal issue with the power relay itself.

 

If an external issue then it would take at least 2 failures at about the same time to cause the servos to keep running with key-off.

 

What is the brake light doing at battery re-connect?-- if ON all the time that tells us one thing, if off then comes on with brake lever/pedal apply that tells us something else.

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What is the brake light doing at battery re-connect?-- if ON all the time that tells us one thing, if off then comes on with brake lever/pedal apply that tells us something else.

 

Howdy DR,

 

As of the day of the failure and Sunday while running the GS 911, with battery reconnected and ignition off, servo's would run but no lights on dashboard.

 

As of the time I write this, reconnecting the battery yields nothing. Turning on the ignition, the servos "spool up" and the "brake failure" light flashes rapidly and the red light below stays lit - no flashing.

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Okay, fuel tank is off and I've found no discernible electrical issues, i.e., frayed or mitigated wiring. :(

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What is the brake light doing at battery re-connect?-- if ON all the time that tells us one thing, if off then comes on with brake lever/pedal apply that tells us something else.

 

Howdy DR,

 

As of the day of the failure and Sunday while running the GS 911, with battery reconnected and ignition off, servo's would run but no lights on dashboard.

 

As of the time I write this, reconnecting the battery yields nothing. Turning on the ignition, the servos "spool up" and the "brake failure" light flashes rapidly and the red light below stays lit - no flashing.

 

Morning Beemerboy

 

When turning ign switch ON & servos start on their own "COULD" point to failed brake switch OR something stuck in the switch area.

 

So check rear switch for something stuck in it or between the reed & stop.

 

Otherwise, either mechanically verify brake switch operation (they should be closed at rest & go open when applied) or get a GS-911 on that bike & read codes.

 

This wouldn't explain key-off original problem but could explain key-ON current problem.

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  • 2 weeks later...

Hey folks, it's been a while since I posted on this thread and I now have an update to provide. In short, I tore into the RT and inspected all wiring, connections, tubing, appurtenance, and just about all other stuff associated with the ABS unit. I found nothing that could be considered the culprit so I made arrangements to haul the bike to an independent BMW shop in west Denver.

 

Within an hour the report back was a bad ABS unit, nothing more specific than that. I asked about my options BEFORE I'd left the shop and was told that they could bypass the ABS and the regular brakes would be fine....I just wouldn't have ABS. My preference was to try to get the bike back to normal with parts cost being the final arbiter. When told that the ABS was bad they also told me that the cost of a new unit was just over $2500 but that they'd found one on eBay for a $239 by it now price. I gave them the go ahead and it'll be there next Tuesday.

 

The story doesn't end there. Upon returning from this year's Un, I'd noticed a strange sensation emanating from the rear of the bike. I'd changed all fluids and filters prior to leaving for the rally and when I got home I drained the FD to check for metal bits but found none. I'd asked the shop to check things out on the bike but didn't tell them of my experience with the FD vibration. Sure enough they reported something unusual and found a bad bearing. My

 

RT has just over 61K miles on the odometer and has suffered all the big ticket items in terms of mechanical issues; prematurely worn splines, ABS unit, FD bearing. I'm the original owner and maintain the bike very close to BMW's standards. I can't say that I'm not disappointed but it's also difficult to dislike a motorcycle that has given me so much pleasure over the years.

 

Okay, sorry for the slight detour in thread topic. I'll do a follow up after I've had a chance to put the bike through its usual paces.

 

Thanks again to all who chimed in with their advice especially Dirt Rider - you continue to provide a wealth of information to so many and are a true asset to this forum!

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