ABS light is on

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I have a 1996 N-reg BMW 328SE Auto. Its ABS light is coming on and staying on while driving. However, using the CHECK button on the computer panel displays 'Check Controls OK'.
I haven't been able so far to test it out on a suitable surface, but should I assume it's broken? If so, is a repair likely to be within the capabilities my local garage (which regularly services the car), or am I going to have to take it to an expensive BMW dealer please?
--
Terry, East Grinstead, UK

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Terry Pinnell wrote:

have you checked that all the brake lights work?
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wrote:

& we had one which did this, as the wiring from the sensor was picking up noise from the ignition, a set of OEM leads cured it.
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This means the ABS system has detected an error. Someone needs to connect up a scanner to find the error.

I would suggest a local independant BMW service guy, not a dealer but someone who has done the BMW training and has the special tooling. You can try your local garage but many of the generic scan tools won't be able to get the error off the system.
Once you know what the actual error message is, then you can find out what is likely to be wrong and then how to fix it. If you're lucky it's just a bad wheel sensor somewhere. --scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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snipped-for-privacy@panix.com (Scott Dorsey) wrote:

Thanks all, appreciate the fast responses.
Booked it in for a scan. The mechanic I spoke to thought it might well just be a wheel sensor as you suggested. One symptom I mentioned to him that I missed from my post was that the light doesn't come on when the engine is started, only when in motion. (And I *think* not when I'm reversing out of the drive.)
--
Terry, East Grinstead, UK

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Terry Pinnell wrote:

the car cant tell whether the wheel sensor is giving a signal till it moves and abs is probably disabled in reverse. So wheel sensor or wiring is certainly high on the list to check.
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The ABS light being on means the ABS will not work -- your tires will lock if you use the brakes in a panic, or on ice even if not in a panic.
ABS looks for a tire to stop turning as you apply the brakes. It it finds one then the brakeing pressure is removed from that wheel for a moment and then is reapplied. The result is that the wheel is allowed to turn so you retain directional control over that wheel. The light being on means the system is disabled and the tire will lock and remain so until you release the brakes.
This is not a fatal condition -- we drove around for decades without ABS systems. Indeed, in the early days of ABS, lots of people wanted information on how to disable them.
In any case, you have a failed speed sensor in one or more of the wheels. Odds favor just one failed sensor, but there are four of them and you have no clue which one. You need a diagnostic device that connects to the Data Link Connector (the round one by the right-side shock tower in the engine bay) to read which one has failed. Replacing a speed sensor is not a difficult task, and one that most people should be capable of undertaking at home.
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On Tue, 04 Jan 2011 09:04:38 -0800, Jeff Strickland wrote:
[...]

No it doesn't.
It means the system "thinks" there is a fault which *might* mean the ABS won't work.
Chris
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much like they were saying:

I've never yet come across an ABS system that didn't fail-safe and turn off completely at the first sniff of a fault.
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On Tue, 04 Jan 2011 18:35:19 +0000, Adrian wrote:

The wiring loom to the dash gets damaged; a short from a live wire connects to the ABS warning light...
Chris
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gurgled happily, sounding

The only safe assumption is that if the light is on the system has disabled itself. If the system turns out to work when you need it, count that as Living Well and thank your lucky star.
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On Tue, 04 Jan 2011 10:51:17 -0800, Jeff Strickland wrote:
[...]

Yep.
But the light being on doesn't mean the ABS *will not* work.
Only that it might not, so shouldn't be relied on.
Chris
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On Tue, 04 Jan 2011 18:57:37 -0000, Chris Whelan

Except that the probability of might is almost certainly well in excess of 99%.
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On Tue, 04 Jan 2011 19:03:34 +0000, Duncan Wood wrote:

So the statement should be "The ABS light being on means the ABS will *probably* not work.
I was just trying to point out that a single indicator light can't be relied upon to show the status of a complex system.
Chris
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On Tue, 04 Jan 2011 19:05:44 -0000, Chris Whelan

It does do a rather accurate job of it though. And the edge case is somewhat pointless to consider.
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wrote:

The truth is that your single data point is not an indicator that the complex system might work.
FOR THE RECORD I have an E36 with the ABS light on, and it's been on for well over 5 years that I know of. My car has a problem with the valve body and I don't care about it enough to fork over $1000. I've driven most of my life in cars that don't have ABS at all, so having a car with ABS that doesn't work is no big deal in the grand scheme of things.
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On Tue, 04 Jan 2011 11:10:13 -0800, Jeff Strickland wrote:
[...]

Ah, I see.
You don't live in a country civilised enough to require your car to have regular examinations to make certain it meets the safety standards the manufacturer built it with.
;-)
Chris
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Jeff Strickland wrote:

that is fine till there is a bad situation. ABS equipped cars (may )have a different brake balance to a non abs car (when the abs is inoperative). I know this for certain from road testing ABS fault vehicles. When full braking is needed you may find that the car rotates rather rapidly. If you intend to go on using your faulty vehicle it would be a good idea to establish which end of the brakes will lock up first. If it is the rear end then it would be prudent to get the abs fixed. If it is the front then you should be fine.
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wrote:

& E36s are notorious for the pressure sensor in the valve block, you can get them reconditioned.
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But, don't believe anything you hear from random people like us on the internet. Go into a parking lot, get up a little speed and slam on the brakes and feel what happens. If the ABS triggers, you'll sure know it. If the ABS activates properly, you won't skid. If it activates improperly you may. Then you will actually know, rather than listening to people like us surmising. --scott
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