ABS light is on

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Chris Whelan wrote:


0.3v ac when spun at 60 rpm on the fronts and 0.4 on the rears
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On Tue, 04 Jan 2011 19:24:01 +0000, Mrcheerful wrote:
[...]

Yep, and usually 0.0vac on the faulty one!
Chris
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The 15 year old BMW 328SE Auto is in the local servicing garage now, awaiting their verdict and quote.
So, although it's now academic, I'd like to pursue this DIY discussion a bit further please, from my perspective as a driver not a technician or regular DIYer. I'm fairly adept with mechanics and electronics, but despite all the helpful advice here there's absolutely no way I'd tackle this myself!
Even if, despite my sore throat and worsening cough, I was prepared to change into old clothing and venture outside where it's cold and raining, even if my drive wasn't steeply sloping (making jacking risky), even if I could somehow find the many hours to clear my garage and get the car into it, or find a flat spot on the narrow road where I wouldn't block other users, even if I successfully jacked up the first wheel without barking my knuckles or other incident ... then I know I'd face various practical issues within minutes:
What oil and dirt-encrusted sensor am I looking for? Where will I find it. Apart from the link Duncan gave for the ABS Sensor: http://www.picoauto.com/waveforms/popular/wave86.html further googling refers to the 'Road Speed Sensor': http://www.picoauto.com/waveforms/Sensors/RoadSpeedSensor/wave129.html so I suspect it won't be obvious which is which.
Once I located it (using lighting under the car, powered via cable from my garage to the road) I suspect I wouldn't find it obvious how to remove the connecting wires. (And, if there are more than two...) But once that's done (assuming my morale is still high, despite this being wheel #1 of 4), hopefully testing for total failure would be straightforward. Although the ABS sensor appears to have a roughly sine output, presumably that would register while turning the wheel slowly, with my DMM set to either DC or AC?
--
Terry, East Grinstead, UK

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Oh dear.
Just got the verdict: "the scanner reports the code indicating that the actual ABS Control Unit chip is faulty..." parts alone would be 895 + VAT = about 1074 ($1670), then fitting (unquoted), then "programming, which would have to be done at a BMW Dealer".
Obviously I'll now have to live with it. At the latest until next September when my MOT is due. Better start looking around ;-(
--
Terry, East Grinstead, UK

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As suggested a few postings ago give this bunch a call and see what they have to offer. Worth just a call surely?..
We used them for our Volvo ABS unit an it was off and back within two days!..
And those figures above where in the same order that we were quoted for the Volvo .. in the end we paid sub 200 quid:-)..
http://www.ecutesting.com/index.html
--
Tony Sayer


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Thanks Tony. I 'phoned them in Nottingham but apparently now need to get hold of the part number before they can advise and quote.
I imagine you dismantled (and re-fitted) the part yourself? In my case I'd get the garage to do it. But, assuming ECU Testing can do it at a reasonable cost, what about this 'programming' step? Did you have to get a Volvo dealer to do that? As you probably saw, my garage says that would be outside their scope.
--
Terry, East Grinstead, UK

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Well you've made a start;)..

I removed it and re-fitted it myself. Nothing other then a Torx driver needed .. total time to remove 5 mins refit 10 mins :)..
No other programming needed. Ask them for their advice there is a very knowledgeable bloke there. In fact I could have done this myself if I'd been so minded after all they are printed circuit boards and they suffer from a lot of "dry joints" i.e. where the soldered joint has fractured.. They are however set in a sealant which is quite hard so I didn't want the damage it any further and as the overall cost wasn't that much let them get on with it:)..
--
Tony Sayer


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On Thu, 06 Jan 2011 12:44:11 -0000, Terry Pinnell

Disconnect the battery 1st, & you're going to refit the same one so you don't need to reprogram anything.
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wrote:

You should be taking that car to a BMW technician.
A BMW trained technician will be able to program the car as part of the service he's already doing. The programming effort takes all of about 5 minutes, but requires a relative expensive computer program. But any good BMW shop will have this equipment because they recognize it is needed to serve their clients.
Having said that, the price you were quoted is about the same as they give us over here.
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On Thu, 06 Jan 2011 09:54:57 +0000, Terry Pinnell wrote:

[...]
You posted this into a maintenance NG, so most regulars might assume that you were prepared to "have a go"; perhaps it might have saved some time and effort if you had been clearer from the outset that you didn't intend to get your hands dirty?
These days, most DIYers will either own a suitable DMM, or would be able to borrow one from a friend. You can't even begin to carry out the most basic electrical fault-finding without one. A suitable one would cost perhaps 40UKP
ABS sensors for your car are around 30UKP,
http://secure.gsfcarparts.com/shop/results.asp
so even if you had to buy a meter, the total cost was only likely to be 70UKP.
If all the sensors appeared OK, and you didn't feel able to investigate further, you would have lost 40UKP, but gained some skills, and a test instrument that might last the rest of your life.
If you genuinely have even basic technical competencies, you could have completed the tests on all four wheels in an hour; it would also give you the chance to check for brake pad and disc wear, split rubbers on suspension and steering joints, condition of brake hoses ect. Then, the next time you service your car, you could elect not to carry out those checks if you felt all was well.
WRT your question about what to look for, image-Googling will give you some relevant hits.
There is also masses of information about testing sensors; eg:
http://www.topbuzz.co.uk/maintenance/testing_abs/testing_abs.htm
Let us know how it pans out.
Chris
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On 06/01/2011 12:03, Chris Whelan wrote:

Sorry to hijack your post - but - could you recommend a DMM? I have a £3 one that I use for continuity/voltage, but it'd be nice to have one that's reasonably versatile should the need arise.
Thanks, Rob
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On Thu, 06 Jan 2011 12:10:38 +0000, Rob wrote:
[...]

How much do you want to spend, what is your level of expertise, and what will be its primary use?
(I'm probably not the best person to answer this; I'm lucky enough to never had to pay for a meter in my life, but I like Fluke!)
Chris
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Even the cheapest DMM has the basic ranges of Ohms, DC and AC Voltage, DC Current and (almost always) a Continuity Tester. I've used my various cheap to mid-range units over many years on my cars. (Mainly when adding gadgets and alarms on early models, before all such desirables came built in!)
Apart from recommending you ensure it has a high DC current range (at least 10 Amps), I can't immediately think of any other must-haves. But I'm not a car DIYer, so maybe for diagnostics etc others here can suggest additional advanced features.
Meanwhile, here are a few, ranging across the price spectrum:
DT830D 2.81 (3.37) http://cpc.farnell.com/1/1/57759-digital-multimeter-continuity-dt830d.html
72-7765 9.79 (11.75) http://cpc.farnell.com/1/1/35468-digital-multimeter-72-7765-tenma.html
72-7735 24.95 (29.94) http://cpc.farnell.com/1/1/45477-digital-multimeter-72-7735-tenma.html
FLUKE 113 94.00 (112.80) http://cpc.farnell.com/1/1/41765-digital-multimeter-fluke-113-fluke.html
--
Terry, East Grinstead, UK

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On Thu, 06 Jan 2011 13:24:06 +0000, Terry Pinnell wrote:
[...]

dt830d.html
Nothing I could add to that, except ISOTECH make some good mid-range ones.
Chris
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On 06/01/2011 14:08, Chris Whelan wrote:

Excellent - thanks both. I don't have a great deal of knowledge of or, frankly, 'head' for autoelectrics. But it is something I'd like to get the hang of, and when I replace my old one (exactly the same as the first in your list) I'll know what to get.
Rob
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Buy the Fluke 77. It has far more digits of precision than you will ever need for auto work, but they are all valid digits and you can drop it and crush it and they will still be good.
You may, though, honestly find that an analogue meter is more useful since it loads the line down more. You can have bad connections with a lot of resistance that seem okay with the high-Z DMM when you measure voltage, but can't actually supply any current. --scott
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On Thu, 06 Jan 2011 09:43:03 -0500, Scott Dorsey wrote:

Nice meter, but in the 200-300UKP price range.
Chris
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Yes, but you can run over it far more than ten times as often as the #20 meter. --scott
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On Thu, 06 Jan 2011 11:34:35 -0500, Scott Dorsey wrote:

LOL!
I worked in industry as an electrical technician; you wouldn't believe how many ways there are to kill an expensive DMM!
Chris
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Chris Whelan wrote:

Like what? A good one will survive up to 600V on any input (including the wrong ones).
A good quality meter (any Fluke, don't need the spendy 77) should last the average jerk a lifetime.
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