• Welcome, Guest! We hope you enjoy the excellent technical knowledge, event information and discussions that the BMW MOA forum provides. Some forum content will be hidden from you if you remain logged out. If you want to view all content, please click the 'Log in' button above and enter your BMW MOA username and password.

    If you are not an MOA member, why not take the time to join the club, so you can enjoy posting on the forum, the BMW Owners News magazine, and all of the discounts and benefits the BMW MOA offers?

ABS Error - missing pin?

johnwraystewart

New member
I just got done finishing up replacing the stainless lines on my R1150RT. Previous threads on my associated trials and tribulations:

https://forums.bmwmoa.org/showthread.php?100578-Advice-on-stuck-stripped-bolts-and-bleed-screws
https://forums.bmwmoa.org/showthread.php?100463-R1150RT-Stainless-Lines

Well, I thought things were going so well this weekend. The bleeding operation, if a bit messy, went well (holy cow, 9 different bleed screws!).

However, I just put things back together and now my ABS light is blinking rapidly... and not engaging the pumps at all. All of which was working before the bleeding operation.

This seems like it has to be electrical... and the only thing electrical I touched was pulling the plug on the ABS pump. Looking at it now, I notice one of the pins is significantly shorter than all the rest. I was putting paper towels in there to clean up spilled brake fluid. Maybe I broke a pin in the process?

I guess my question is - these pins should all the same height, right??

And the follow up - how screwed am I here?

IMG_1995.jpeg
 
I think before pulling on the pin I’d probe the female portion of the connector to see if it holds a broken-off bit.

Best,
DeVern
 
Check your brake switches (front and rear). If the brakes are applied (switches activated) before the ignition is turned on, it will produce your problem.

I changed brake lines on a client's R1150RT and has this issue. Found out the rear brake switch was very sensitive and lighting the brake light in it's retracted position. I adjusted it and it solved the problem.
 
So, I did tug on the pin with a pliers with no detectable movement.

I didn't see a pin stuck in the female side. So I took a needle, shoved it into the connector, then snipped it off at about where I thought it needed to extend to.

I plugged it all back in and it makes a Good Enough connection; no errors, brakes work great!

Yet another ugly hack, but in looking at what these ABS units are going for on ebay ($1k!), if it works, I'll ride it.
 
So I took a needle, shoved it into the connector, then snipped it off at about where I thought it needed to extend to.

I plugged it all back in and it makes a Good Enough connection; no errors, brakes work great!

My compliments on your ingenuity, sir. :thumb
 
So, I did tug on the pin with a pliers with no detectable movement.

I didn't see a pin stuck in the female side. So I took a needle, shoved it into the connector, then snipped it off at about where I thought it needed to extend to.

I plugged it all back in and it makes a Good Enough connection; no errors, brakes work great!

Yet another ugly hack, but in looking at what these ABS units are going for on ebay ($1k!), if it works, I'll ride it.

“More than one way to skin a cat…”

Do yourself and any future owner a favor and document your fix in the owner’s manual, and maybe even attach to the connector a tag telling a future tech to “check owner’s manual before disconnecting”. No sense risking a repeat puzzle if that connector gets pulled and your fix drops out unnoticed.

Best,
DeVern
 
Alas, on my first ride of more than a few blocks, the ABS errored out again. I'll say even with "residual braking", the front brakes work DANG well (the rear brakes seemed much more affected).

Going to have to try Plan B, but not sure what that is yet.

I'm thinking I'm going to give it another pull. Maybe what I did was, instead of snapping the pin:

- Paper towels bent the pin.
- Pushing the connector on pushed the pin down.

This makes sense in that the depth of that short pin is about where it seems like the connector extends to.

I did pull up medium hard on that pin, with no apparent movement. I'm loathe to yank too hard and mess it up worse, but I think next step is to yank harder than medium hard.
 
Do not yank it, a steady straight even pull will do it.

This is what it looks like from behind.
I would pull the cover and carefully push from behind and have someone pulling on the other side.
Note that the cover screws are tamperproof triangle or tamperproof 5 point torx
 

Attachments

  • 20210804_142819.jpg
    20210804_142819.jpg
    249.8 KB · Views: 104
Thank you GSAddict.

Last night I took a needle nosed vice grip, and then slowly but firmly pulled up, and got the pin back out! Seems like things are working (knock wood).
 
Good luck. I work with connectors for a living (avionics) and card edge connector pins are soldered to the board. Pulling or pushing on them frequently breaks the solder joint.
 
BAH, boo, crap.

So after "fixing" the pin last night, it seemed to go together fine. I rode into work (a few miles) and then at lunch, on my way back from the sandwich shop, the bloody ABS light came on again. It seemed to coincide with a bump in the road, but maybe that was just coincidence.

It DID seem like the brakes were working fine - good stopping power, and I can hear the servo assist on the brakes. Even when powering the bike off, then on, the error persists. You can hear something going on in the ABS unit. I took a video of the result on power-on today after getting back from lunch:

https://www.youtube.com/watch?v=sE4hKTG-NwQ

I'll check fluid levels, etc. Anything else I should check? Sounds like maybe I need to hunt up a code reader (oof those look expensive)?

I would pull the cover and carefully push from behind and have someone pulling on the other side.
Note that the cover screws are tamperproof triangle or tamperproof 5 point torx

GSAddict - I see mine have the triangle screws; I would have to seek those out. Do these look right?
https://www.amazon.com/Silverhill-Tools-ABSTR6-Triangle-Power/dp/B07FM9D98W

Is it possible to open this thing up without completely removing from the bike, and I guess draining all the brake fluid from the ABS unit?
 
Another data point - I went to ride home after work, and the bike came up with no errors; worked fine.

For about two miles. I was giving it the beans a little bit and the error came back.

And indeed it seems that servo brakes are intermittent. I was turning into my street off the main drag, and it was clearly on "backup" braking. Had to squeeze it much tighter, at which point THEN the servo kicked in. Was a bit of a pucker up.

Oy.
 
Bit style below.
If you loosen the bottom mounts you may be able lift high enough to remove.
The screws are usually loctited with blue, they are not the easiest to remove.
I have had to cold chisel the sides of the heads to remove. Replace with M4 phillips.
I always remove the module, its simply easier to work on.

The pin in question is #7 which goes with a yellow/black to the foot brake switch and returns with a yellow/green to pin 41
Make sure the switch is operating correctly
Closed when at rest
Open when actuated.
Reverse failsafe logic.

Check for a cold solder joint on pin 7 to the board. You will need to unplug all the cables for the module and the unscrew the board from the cover to expose.
take lots of pictures so there will be no confusion upon reassembly
 

Attachments

  • Triangle bit.jpg
    Triangle bit.jpg
    145.1 KB · Views: 91
  • Triangle screwt.jpg
    Triangle screwt.jpg
    121.9 KB · Views: 94
Again, thank you GSAddict.

Bit style below.
The pin in question is #7 which goes with a yellow/black to the foot brake switch and returns with a yellow/green to pin 41
Make sure the switch is operating correctly
Closed when at rest
Open when actuated.
Reverse failsafe logic.

I will check this next.

To make sure I understand you - this would be on the cable bundle / plug that plugs into the ABS unit, right?

In other words, it sounds like testing connectivity between the holes in this plug on #7 and #41, I'm looking for it to be closed when at rest, and open when I press the foot brake.

I'm a bit confused in that I don't see anywhere near 41 pins on that thing - these must have some numbering scheme I'm not aware of? Is there a diagram you can point me at?

(Edit)

I did just find this, which is super-helpful:
https://www.yumpu.com/en/document/v...lectrical-schematic-p-1-of-3-v31-1-mac-pacorg

... although I don't see yet how to tell which wires are which in that connector (7 vs 41)

Check for a cold solder joint on pin 7 to the board. You will need to unplug all the cables for the module and the unscrew the board from the cover to expose.
take lots of pictures so there will be no confusion upon reassembly

And presumably disconnect all the brake fluid connections? I guess cork them up somehow so they don't leak everywhere? The DOT4 mess is what scares me about this operation, not the electronics.
 
So, interestingly (well, to me)... whenever the bike sits for some time, it seems to come back on with no ABS error.

It's only after driving it for a few miles that the ABS error comes up (and servo-assistance cuts in and out). The light are:

> Gen ON, ABS flashes at 4Hz =At least one brake circuit in residual braking function mode.

About to begin disassembly of the tupperware and gas tank. Again.

Is it possible this is just a low fluid level? I think NOT, because when I had that previously, it was a flashing between the ABS and Gen lights, not like this (fast flashing of ABS, Gen on solid).

It seems weird to me an electrical issue would exhibit this behaviour (only erroring out after riding for a bit). I'd expect it to be more consistently broken (or not), or at least not consistent in how the issue is displayed. Not always resetting itself, then triggering again after a bit of a ride.
 
Back
Top