ABS lights flashing...still

[jshuck]

Here's my story 02 1150 GS 50K miles

The battery is a 2 yr old gell showing 12.85 volts. I keep it on a tender. I can reset the ABS by doing the pin 2 and pin 4 jumper, key on and holding the ABS button for 60 sec. reset. After I do this, the bike starts well and I get both lights flashing in tandem like they should.

At roll away, I get the usual kerchunk and the lights start alternating flashing. I took the bike in to the dealer and he reset the modulator piston with the GT1 tool; what ever that is. This worked at next startup, but the next day everything was the same. Here's what I have done:

1. Bled brakes at the wheels and at the ABS unit. I had done just at the wheels about 10K ago, but not at the ABS unit. Despite this, the fluid looked clean at the ABS and I ran alot of fluid thru the system. No bubbles, feels solid.
2. Checked the airgap at the wheel speed sensors. The rear one seemed a little wide, so I removed a shim and got it within spec. I also checked the ABS rings and cleaned the sensors. This bike had a Final Drive bearing replacement, so I thought the shims for the final drive might have moved the wheel out a little. Both sensors are within spec now.
3. Checked the wheel speed sensors for continuity. No open circuits and both read about 320 ohms, which appears to be within spec.

So... The service manager at the dealer said when he reset the piston that I might need a pump. I'm not to hot on droppping $1500... any ideas???
Thanks John Shuck

[SIBUD]

Here's my story 02 1150 GS 50K miles

The battery is a 2 yr old gell showing 12.85 volts. I keep it on a tender. I can reset the ABS by doing the pin 2 and pin 4 jumper, key on and holding the ABS button for 60 sec. reset. After I do this, the bike starts well and I get both lights flashing in tandem like they should.

At roll away, I get the usual kerchunk and the lights start alternating flashing. I took the bike in to the dealer and he reset the modulator piston with the GT1 tool; what ever that is. This worked at next startup, but the next day everything was the same. Here's what I have done:

1. Bled brakes at the wheels and at the ABS unit. I had done just at the wheels about 10K ago, but not at the ABS unit. Despite this, the fluid looked clean at the ABS and I ran alot of fluid thru the system. No bubbles, feels solid.
2. Checked the airgap at the wheel speed sensors. The rear one seemed a little wide, so I removed a shim and got it within spec. I also checked the ABS rings and cleaned the sensors. This bike had a Final Drive bearing replacement, so I thought the shims for the final drive might have moved the wheel out a little. Both sensors are within spec now.
3. Checked the wheel speed sensors for continuity. No open circuits and both read about 320 ohms, which appears to be within spec.

So... The service manager at the dealer said when he reset the piston that I might need a pump. I'm not to hot on droppping $1500... any ideas???
Thanks John Shuck

It's the battery.

[jshuck]

Really?? why do you say that? The bikes starts fine and the lights don't do their dance till I drop it in gear and roll away. Then I get the clunk and the lights do their dance.. I have had a low battery flashing light dance before, but that was after I attempted start up... This seems different. Thanks for yor reply... john shuck

[bmwmick]

Really?? why do you say that? The bikes starts fine and the lights don't do their dance till I drop it in gear and roll away. Then I get the clunk and the lights do their dance.. I have had a low battery flashing light dance before, but that was after I attempted start up... This seems different. Thanks for yor reply... john shuck

Sounds to me like a failing Hydro unit. If you are getting the 'piston fault' error, it's most probably a failing mechanical assembly inside the unit. When it initializes, the control unit monitors the speed with which the pistons are moved. If either piston fails that movement test, it sets a fault. This fault is hardly ever repairable.

I've disassembled a few ABS-II Hydro units and found very similar mechanical problems in every one that had a piston fault. The big DC motor in the unit spins a main shaft that has two electromagnetic clutches (like your AC clutch on the car).
There are two chains wrapped around the clutch driven pulleys and those chains pull the pistons to relieve pressure in the front or rear circuit. If the chains don't move smoothly over the roller or if one of the clutches is slipping, it can cause a fault.

You may be able to find a good used one from a wrecked bike or try www.beemerboneyard.com

[jshuck]

the more I chew it over, the more I think you might be correct. I hardly ever activated that ABS unit so I guees I should have to keep it working properly. To me..if you have to use it..you're over your head and I try not to get that way. We'll find out when we get it in to the dealer. Thanks for your reply... john shuck

[Andy VH]

I bought a salvaged ABS modulator on ebay for $250, and replaced it myself on my 94 R1100RS. Then I rode the bike to my dealer and had the modulator "identified" on the bike. All is well again.

The original modulator had quit working. The dealer I used to go to, claimed I had done too many low-voltage cold-morning starts (before I had a Battery Tender) and it "burned in" the low-voltage fault permanently into the modulator.

Not sure if that is likely or true. But my ABS works fine now.

[bmwmick]

the more I chew it over, the more I think you might be correct. I hardly ever activated that ABS unit so I guees I should have to keep it working properly. To me..if you have to use it..you're over your head and I try not to get that way. We'll find out when we get it in to the dealer. Thanks for your reply... john shuck


John,
Yes, you should test the ABS just so you know what if feels like when you use it but the entire circuit is exercised each time it initializes and then periodically while you are riding. You'll notice it when you come to a stop after a prolonged run. As soon as you pull away, it will go through the self-test.

Good luck at the dealer and please post the fault code they report.
I'm betting they see a code 7 (control unit)or code 12(piston fault).

[jshuck]

I didn't realize that the ABS activates itself at startup. I just thought it tests. I had gotten the "ABS shutter" during very aggressive braking only a few times during my tenure with the trusty steed. Guess it's just one of those things. Beemerboneyard is zero stock on the modulators, so we'll see what happens at the dealer. Thanks john shuck

[bmwmick]

Good luck!:lurk

[SIBUD]

John,
Yes, you should test the ABS just so you know what if feels like when you use it but the entire circuit is exercised each time it initializes and then periodically while you are riding. You'll notice it when you come to a stop after a prolonged run. As soon as you pull away, it will go through the self-test.

Good luck at the dealer and please post the fault code they report.
I'm betting they see a code 7 (control unit)or code 12(piston fault).


I am also interested in the fault code. Inquiring minds want to know. :lurk

[SIBUD]

Really?? why do you say that? The bikes starts fine and the lights don't do their dance till I drop it in gear and roll away. Then I get the clunk and the lights do their dance.. I have had a low battery flashing light dance before, but that was after I attempted start up... This seems different. Thanks for yor reply... john shuck

Re reading your post, I agree that it is not the battery.

[scalzitti]

Looks like I have the same problem.

It started in April. I set off on a long day ride and the ABS lights were flashing - no biggie I thought - the battery's just low, but will charge up by the time I make my first gas stop. Those ABS lights flashed for over 700 miles that day!

When I got home I put the bike on the charger and the next morning verified that the battery was fully charged. I drove off and the ABS lights were still flashing hours later.

I drove to the dealer who reset the fault code and off I went. He warned me that the ABS unit may be bad, but I was convinced it was either the battery (new last year) or the charging system.

3 months later and the fault keeps returning - looks like a big repair bill is in my future. The dealer has the bike.

My ol' GS has over 80K miles and still runs great - think I'll keep her!

[jshuck]

An update on my flashing light on my 1150GS. The codes read that the ABS pump had failed. They had used the GT1 device to reset the codes and reset the pump, but it lasted only a day. Looks like the code was a piston fault. I just got it back from the dealer this morning. All is well now, but the pump had in fact failed. Got a new one now and the bill was $2600. That is not a mis-print. I do all my own work, but this one was beyond me. I almost considered parting the bike out, but this is a great bike, before the servo brakes and other stuff. do-do happens. john shuck

[SpongeBob Squarepants]

An update on my flashing light on my 1150GS. The codes read that the ABS pump had failed. They had used the GT1 device to reset the codes and reset the pump, but it lasted only a day. Looks like the code was a piston fault. I just got it back from the dealer this morning. All is well now, but the pump had in fact failed. Got a new one now and the bill was $2600. That is not a mis-print. I do all my own work, but this one was beyond me. I almost considered parting the bike out, but this is a great bike, before the servo brakes and other stuff. do-do happens. john shuck

Hey, thats a good deal! I have the same problem with my 02 R1150RS. Pump fault. My local BMW Stealer quoted me $3600 for the ABS modulator, and 5 hours labout at $95/hour. $4100 + tax. Of course I live in Canada and BMW Canada thinks I have no options but to hand their stealer the work.

Can I ask how many hours labour you were quoted?

[jshuck]

looks like 4 hours. I'm not sure what his labor rate is, but the pump was 2,065.00. Works fine now.. They warned me about installing a used unit unless it is an exact replacement. He has had trouble in the past adapting an S or RT pump to a GS. I have only used the ABS maybe once or twice, but I figure if it saved my butt once, it's worth $2600. Good Luck.. John Shuck

[SpongeBob Squarepants]

John,

Thanks for the update. It appears that the R, the GS, and the RS use the same pump, as they all have the same part number. The RT has fully integral brakes, not partial like the other models, so the pump has a different part number. I wonder if thats what the warning is about. Not sure what I will do, but even if I win the lottery tomorrow, I won't be handing over $3600 to BMW Canada. I plan on letting them know that, but no one answers the phone at customer service, and they don't return the call!

[DPeakMD]

Those $$$ are scary! I skipped doing my own brake fluid change and took it to the dealer, figuring if they messed up something, they would be responsible to fix it. Not me as if I did it myself.

Now I'm worried because my "Brake Failure" light keeps coming on and I'm worried they did screw something up!