iABS woes on a K1200RS (somewhat long, sorry...) - K-Bikes.com - Excellence in Motion
 
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post #1 of 6 (permalink) Old Mar 25th, 2018, 2:46 pm Thread Starter
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iABS woes on a K1200RS (somewhat long, sorry...)

OK so here's the story:

I have a K1200 RS, picked up last September (2017). It has been showing intermittent failure of the rear brake servo (iABS partially integrated is fitted). I have tried the following:

Change of all brake fluid by trusted independent BMW mechanic. And then made sure DOT4 fluid in all 3 reservoirs was topped off to the max, myself, just to make sure.
Checked resistance of front and rear ABS sensors. All good.
Checked continuity of front and rear brake switches. All good.
Checked (and then changed anyway) rear brake/tail bulb.
Checked load at starting on battery. All good.
Hitting the unit with a piece of wood and an extension bar (the theory being I could unstick a sticky pressure relief valve, seen on photos/schematic by people who've actually dismantled the things). This would work for any distance between 200 yards and 20 miles before the rear servo stopped again.

Trusted independent BMW mechanic says: Unit buggered probably, take it off and convert to hard non-ABS brakes. Main BMW dealer says nothing we can do, you probably need a new mega-expensive iABS unit, but we'll clear the faults off the computer for you (as the brake system is working when I visit them, obviously...)

Since BMW dealer cleared the computer... No problems. iABS unit works perfectly.

My question is, why? The only possible answer I found was on page 267 of the Clymer manual, where it says (in the bit about the Throttle Position Sensor reset):

'...if any fault codes were set before the battery was disconnected, they will be reset as soon as the motorcycle is ridden a short distance.'

I first saw the intermittent failure from the bike when first riding it, and noticed that, although the bike was in good condition generally, it showed definite signs of having been left standing still in the elements for too long.

And I disconnected the battery twice to fit things like Optimate cables, and check connections were good. Have I been basically 're-awakening' old fault codes every time I get on the bike? Is that the reason for the intermittent failure? Now the bike has been used a bit, and had its fluid changed, do the brakes actually work fine, but with the 'ghosts' of old fault codes deciding to cut out my rear servo? Why should a simple clearing of the old fault codes lead to such a dramatic improvement (over 100 miles trouble free, which hasn't happened in ages)?

Do any of you fine people know the answer? Despite being blessed with both an independent BMW mechanic, and a main dealer within a few miles of me (I'm in the small UK), knowledgeable guys on the web have managed to give more tips than them and the Clymer manual combined, so far. Thank you for reading this far, in any event!

PS: If anyone knows how to 'hack' the iABS unit electrically (using connections at the diagnostic plug, for example), I'd be interested to know, as the rest of the internet seems to think it's impossible!
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post #2 of 6 (permalink) Old Mar 26th, 2018, 1:47 pm
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Fault codes have no effect on the sub-system in question (IABS unit) They merely are there to help diagnose the problem. If you or a dealer clears the codes, the only way one can return is if the problem that triggered it in the first place re-occurs. I'm not sure what you want to accomplish by any iABS "hack" but here is an old link to someone that removed the ABS pumps and retained the use of the circuit board. On Two Wheels: ABS removal : epilogue (hopefully)
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post #3 of 6 (permalink) Old Mar 27th, 2018, 5:24 am Thread Starter
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Hi, and thanks for your reply (and getting to the end of my post!)

Yes, I'm well aware of what the fault code system is supposed to do. I'm just absolutely baffled as to why clearing the old codes resulted in such a dramatic improvement when everything else I'd tried made no difference. (I forgot to mention that I'd checked rear ABS sensor was clean and correct also...)

The only reason I was thinking of an electrical hack to clear the codes is that I've already used a similar tip from an LT rider on this board to reset a faulty low-fuel light with good results. A similar process for ABS fault code clearing would save me the equivalent of 35 bucks paid to the dealer, even if they are only 5 miles away!

That said, if it faults again, I'll probably get an ABS-ectomy anyway - too tired of checking everything multiple times to find elusive faults that apparently aren't there half the time !

Thanks again,

PJ
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post #4 of 6 (permalink) Old Apr 19th, 2019, 10:55 am
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disconntect teh ABS2

Quick fix for the ABS2 system on the K1200RS:p/n 34327661752 (order 2 ea). This part plugs into the hydraulic system and deletes the ABS hydraulics. Same part front and rear. Once I have that done, I'll dip into the electrics of the system to get rid of the flashing lights - or simply remove the bulbs. The ABS unit itself can be removed, but the electronic harness must remain - at least to keep your speedometer working.

I cannot say how available these $15 parts are - but BMW made them for SOME reason! Another option is to get custom brake lines to connect the brake directly to the actuator. Same sort of process to the above, so the ABS servo can be removed, but the harness should be kept intact.
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post #5 of 6 (permalink) Old Apr 19th, 2019, 12:34 pm
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Quote:
Originally Posted by F1Boss View Post
Quick fix for the ABS2 system on the K1200RS:p/n 34327661752 (order 2 ea). This part plugs into the hydraulic system and deletes the ABS hydraulics. Same part front and rear. Once I have that done, I'll dip into the electrics of the system to get rid of the flashing lights - or simply remove the bulbs. The ABS unit itself can be removed, but the electronic harness must remain - at least to keep your speedometer working.

I cannot say how available these $15 parts are - but BMW made them for SOME reason! Another option is to get custom brake lines to connect the brake directly to the actuator. Same sort of process to the above, so the ABS servo can be removed, but the harness should be kept intact.
If indeed you are referring to a K1200RS of 1998-2001 (in USA Market), then you are correct this is earlier/simpler ABS2 system that is fairly easy to remove or bypass. On these, there is no need to keep any part of the ABS module electronic active.
These earlier K1200RS models have:
- separate speed sensor on top of rear-drive
- brake switches that are wires normally and are not monitored by the ABS modulator.
- neither is brake fluid level monitored by the ABS system

HOWEVER, most post about ABS problems here are about later models having iABS with servos (K1200RS of 2002-2005 in USA). These are very different and difficult to bypass "cleanly". BMW has also use a very similar iABS system on many other 4 cylinders and Boxers models until late 2006.

Adding 2 bypass rigid hoses you have mentioned is ONLY one piece of the whole puzzle on these iABS system.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
John (Montreal, CANADA)
K1200RS (2002 IceBlue/Red - 95,000 miles)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Last edited by sailor; Apr 19th, 2019 at 12:40 pm.
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post #6 of 6 (permalink) Old Apr 20th, 2019, 12:41 pm
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2003 K1200GT fixed with rear brake switch adjustment

Hi PJ,

I had an ABS and servo problem on my 2003 K1200GT bike the other day. Even with the GS911 no codes were found.

The problem was a quick flashing light and manual mode brakes. No Whizzy noise etc.

The fix is to pull up the rear brake pedal before starting the bike. Make sure it is solid, then turn on the key, let the computer do its checks. If the brake light starts quick and then slows to normal blinking you are good. Start the bike, roll it and the abs is normal. The servo noise also is present with the slow blinking light.

My actual problem was the rear brake was not touching the micro switch enough. I adjusted the set screw some but every once in a while, I have to pull up with my heel before starting the bike. It has no effect during the ride using the brake etc.

So check the rear brake pedal switch.

Other issue can be low brake fluid and low battery at 10vt instead of 12+vt

Keep hunting. Unlikely it is that expensive $3k part everyone wants to sell you.

Regards John
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