Trying to trace an ABS problem. Think I read the fault code correctly ?? as number 4, rear sensor(seems about right as ABS not working at the rear after road test). I want to check through the ABS module/brain but I can't seem to find it. Where is it located on the bike ? signs are - ABS light flashing, hazard light on and wont reset. HELP please.

1990 K100 LT it should be in the rear duck tail, access under the seat at the rear. It may [should] have two rubber straps holding it in place. If its ex police it could be under seat. Even unplugging and reconnecting may help. Not sure about how the reset is done.

Keep us posted. Presumably bike is still all going ok?

Many thanks for that. Derrr, never looked there.....everywhere else ! Also, could you help me with the ABS relays(colour codes etc) and the layout of the ABS relays in (I'm guessing)in the tray at the rear and under the petrol tank please, many thanks.
Brakes are working OK, no ABS at rear, haven't checked the front(to much of a chicken for that one).

The ABS relays are blue and under the tank.

many thanks RicK G

Hi Silver Fox, I see in your intro post you mentioned the ABS sensor gap. Here is a photo of the sticker showing the gap dimensions from the front end of my K75 - I assume the rear sensor would be the same and likewise the K100 would be the same as the K75.



Cheers

thanks for that.

Before you say thanks, remember that is for a K75, others seem to be different. The K1100 manual shows 0.5 mm for front and 0.6 for rear!

K1100 is 16 valve engine and I think the ABS is a bit different.

I suspect K75 and K100 8 valve may be similar as the final drives are same only with different ratios. But the upgrade to 16 valve also changed the rear end to Paralever.

BobT wrote:Before you say thanks, remember that is for a K75, others seem to be different. The K1100 manual shows 0.5 mm for front and 0.6 for rear!

That depends on which model you have. ABS I or ABS II?

RicK G wrote:

BobT wrote:Before you say thanks, remember that is for a K75, others seem to be different. The K1100 manual shows 0.5 mm for front and 0.6 for rear!

That depends on which model you have. ABS I or ABS II?

And then we have early and late ABS II, different sensors and different gaps.

BobT wrote:Before you say thanks, remember that is for a K75, others seem to be different. The K1100 manual shows 0.5 mm for front and 0.6 for rear!

The sensor gap for K75 & K100 (2 valve) front and rear is the same...as per Gaz's picture, the gap should be 0.35 - 0.65mm.
Being a non-contact sensor there isn't any reason why, once correctly shimmed and torqued up, that the gap would change in use. Having said that, I had an intermittent fault on my '90 LT rear sensor a while back - it worked OK, but would then go into warning if I got above 5000rpm. When I checked the sensor gap, I found it was way out of spec - when I shimmed it correctly, I had no further problems with it.

More recently, I had a rear sensor issue on my '89 LT - that proved to be the rear sensor plug (right hand side of bike, behind side panel near coolant expansion bottle) which had got a touch of corrosion on the pins - a quick does of deOxit cured that! That's where I would start looking, rather than the ABS brain... Until the fault condition is fixed, of course, the ABS brain will not reset - which can be really frustrating if there are two or more simultaneous faults...you fix one and then it tells you about the next one!

It is always possible that your rear sensor has gone cactus - and needs replacing. The old ones can be a sod to remove if they haven't been disturbed previously - the aluminium body can stick solidly into the steel brake calliper carrier and the torx head bolts can be problematic too.

thanks for the info and the pointers, will try to crack it tomorrow. I will keep you posted......

Ok, did the sensor gaps on front and réar, i can confirm rear abs Is working but Still lights flashing and won't reset Tried to read the diagnostic with a multi-meter but its very difficult to read Accurately. The varying voltage readings dont seem to répeat in any readable order. Any help or suggestions please....

Sorry, using à french keyboard with auto-correct

If the lights are flashing the ABS will not be working
http://bmwk10075abs1fix.web.fc2.com/ This site gives you all the info needed.

rear abs wasn't working, but is now, since I adjusted the gap. But a problem persists, so I'm guessing the problem now lies with the front abs.

Silver Fox, are you using an analogue voltmeter to read the pulses for the error code?

The reason I ask is that Toshi mentions an analogue meter or a fast response digital volt meter and I initially tried to use my Fluke digital meter (very good quality if you are not familiar with the brand) and found it very confusing to try to count the pulses. I then turned to my very old good quality Peak analogue meter and the stream of pulses were easy to read. The stream of pulses would be repeated after a small interval so I would leave it connected and count a few sets of pulses to be sure.

Just my experience on my K1100 a few years ago - haven't had any ABS issues for a long time.

Cheers

Just to be clear you don't count the pulses but the number of times the light turns off or as more commonly called the dips.
If you count the pulses you will come up one short so a 7 will appear as a 6.
And like I said If the lights are flashing the ABS will not be working

If the pistons are stuck in the calipers would this give rise to an abs hazard light problem, i réalisé the Breaking capability will be/Is none to good. Abs rear is working !

If the pistons are stuck in the callipers, then your brakes will not be good at all - it can happen, especially if a bike has stood neglected for a long while (and the pads can bind on the discs too), but that will have nothing to do with the ABS warning light. You can buy replacement calliper pistol and seal kits at a fairly reasonable price from the usual dealers and it is not too hard to strip down the calliper, clean it up and fit them.

The ABS system senses the speed of the front and rear wheels and, if it detects that one is going slower than the other (because you have applied the front or rear brake harshly and are about to lock up that wheel) it activates and tries to stop the wheel from locking up by relieving some of the hydraulic pressure in the brake line. Normally, both wheels turn at the same speed of course! It is quite easy to cause the ABS to activate on the rear wheel, by a little over exuberant use of the rear brake pedal, especially on wet roads or gravel. It is not so easy to activate it on the front wheel (I did once when I braked very hard, so know that it works!).

If you are sure the rear sensor is correct now and the ABS light is still not clearing (I thought that this condition meant that the ABS system would not activate - so I wonder how your rear ABS can be said to be "working"), then you must have another fault to clear. Try resetting the ABS brain several times to see if you can clear the fault. Have you managed to read the fault code that the brain is still giving you - that'll be a big clue as to where to look next.