1994 K1100RS ABS Fault?

I’m looking at a 1994 K1100 RS, with a ABS fault.

The owner tells me that occasionally, the ABS lights will start to flash, after starting off, and riding several miles. Dealer told him that the ABS is good, but this is happening due to low battery voltage.

So, is the dealer correct in diagnosing this prospective K1100 RS ABS ?

My only experience with BMW ABS faults, are relegated to my R1100 RS. When my battery is beginning to go south, The ABS light simply stays lit, after starting.

If the ABS light flashes on startup, but then after riding a few miles the engine is restarted and the light stays off that is a low voltage fault. As far as I have been able to determine the low voltage fault is the only fault that will reset itself.

Did you mean to post in the K-bike section? If so, a mod can move it for you so it gets more eyes on the problem.

How the lights are flashing makes a difference, and can point to any possible problems. A good source for the light codes is here. Let us know which fault pattern is showing on your bike.
Best,
DeVern

GTRider said:

Did you mean to post in the K-bike section? If so, a mod can move it for you so it gets more eyes on the problem.

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I will move it a bit later
OM

Omega Man said:

I will move it a bit later
OM

Click to expand...

Thanks, my bad. Meant to go in the K bike section.

Thanks you OM

So this is what the owner is telling me. He starts the engine on his 1994 K1100 RS, and the abs lights will extinguish.

It is only after traveling several miles, that the ABS lights begin to flash. He is not stopping and restarting the engine. The lights start to flash as the bike is progressing, with the engine continually running. So I am questioning whether this is caused by insufficient battery voltage, ie: a falling battery. Or, is this something else in the ABS system.

The owner is able to reset the lights by doing a connection to the 3 pin plug under the seat. His dealer gives the ABS a clean bill of health, and says the issue is related to the battery power.

PGlaves said:

If the ABS light flashes on startup, but then after riding a few miles the engine is restarted and the light stays off that is a low voltage fault. As far as I have been able to determine the low voltage fault is the only fault that will reset itself.

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walshj1024 said:

So this is what the owner is telling me. He starts the engine on his 1994 K1100 RS, and the abs lights will extinguish.

It is only after traveling several miles, that the ABS lights begin to flash. He is not stopping and restarting the engine. The lights start to flash as the bike is progressing, with the engine continually running. So I am questioning whether this is caused by insufficient battery voltage, ie: a falling battery. Or, is this something else in the ABS system.

The owner is able to reset the lights by doing a connection to the 3 pin plug under the seat. His dealer gives the ABS a clean bill of health, and says the issue is related to the battery power.

Click to expand...

Quoting from Anton Largiader’s site that I linked to in my previous post:

“ABS2 was used on K1100 from 1994 onwards, R1100RS/RT/GS/R, and early R1100S, R1200C, R1150GS, and K12 models.* The K11 ABS2 uses the same two warning lights as ABS1: the ABS light and the bulb monitor light. On Oilheads and K12s, it has two distinct lights of its own. At key-on, the two lights will flash together and continue to do so until the self-test is complete (which doesn't happen until you start to ride away), at which time they extinguish. If the self-test fails, they will begin to flash alternately. The exact moment when the fault happens will help you know what caused it: if it happens before you start the engine it is an item that is tested at power-up. If it fails when you start the engine, it is almost certainly low battery voltage. And if it fails when you ride away, it's probably a modulator or a wheel speed sensor.

Sometimes ABS2 will fault without showing a fault code that you can read without the diagnostic computer.”

Based upon Anton’s comments it sounds like an issue not with battery, but with the modulator or wheel sensor. Testing the battery is simple: have it load tested at a local auto parts store, or replace the battery with a new or borrowed-but-known-good unit. With wheel sensors, the first think to check is the spacing from sensor ring and the straightness of the sensor ring. If those are good then a sensor could be suspect-but that should throw a fault code. Another possibility with a bike that vintage is a breakdown in the wiring leading to an open or shorted sensor circuit when the bike is warmed up and underway. As per Anton’s note, you may have a case of faulting without throwing a code that can only be read on the BMW diagnostic computer, which increases the difficulty of diagnosing.

I’d settle the battery question first as it is so common an issue, then check sensor spacing and sensor ring. Let us know what you find!

Best,
DeVern

walshj1024 said:

Thanks, my bad. Meant to go in the K bike section.

Thanks you OM

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Omega Man said:

I will move it a bit later
OM

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Good luck. Added a bit to your title- for clarity.

OM