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Audi A4 1996-2001, S4 2000-2002 (B5) A4 Wiring Harness Problem(?)


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Last Post: Aug 11, 2006 8:26 PM Last Post By: Audi.Lover.Hater
jimharper

Posts: 6
Registered: 12/09/03
A4 Wiring Harness Problem(?)
Posted: Aug 2, 2003 3:07 PM
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I have a 1999.5 1.8 Turbo Quattro (VIN WAUB28D6XA243016) whose ABS/Brake warning lights come on for awhile, but sometimes, not always, later on, after the vehicle has been in the garage overnight the warnings are out.

But then the lights come back on for no obvious reason while driving under ordinary conditions (i.e. not braking) or just sitting with the power on for testing.

When the warning lights are out, VAG-COM can talk to the ABS controller (and sees DTC 1203), and check various outputs, etc. But when the warning lights are ON there is no communication at all to the ABS - VAG-COM acts like the ABS controller is unplugged. Other controllers, e.g. engine, transmission, etc., but not HVAC (see below), respond normally whether the ABS is talking or not.

When I unplug (remove) the instrument cluster, thinking there may be a problem there, then the ABS unit never responds to VAG-COM.

If the instrument cluster is in place, but the ABS unit is unplugged, the instrument cluster responds just fine to VAG-COM.

Regardless of what the state of the ABS is, whenever VAG-COM tries to connect with the HVAC controller, it gets the VAG number (8D0 820 043 N) back, but then always fails due to "Excessive Comm Errors."

Without going through the details here of the tests from the Bentley CD-ROM that I ran, I now suspect that I MAY have some sort of short/open/ground problem in the instrument panel wiring harness. I see in the Bentley wiring diagrams (e.g. No 58/1) that there are connectors IN the wiring harness (e.g. A2, A19, A91) but find no indication of WHERE they are in the harness, their color, pin count, etc. or any other clues to identify which is which, let alone find them to begin with.

Before I start randomly dissecting the harness and/or removing more pieces of my dashboard (only the instrument cluster is out thus far) I'd hope for more information about the harness, it's routing, connectors, etc.

Questions:

1) Am I missing something obvious here?

2) Anybody else seen similar behavior (beyond that described in the earlier post named "ABS Controller)?

3) Does it make sense that the ABS can sometimes talk to VAG-COM when the instrument cluster is in place, but never when the instrument cluster is disconnected?

4) Is there some document that shows the instrument panel wiring harness routing and more details about it, such as what connectors are in it and where? Is it in the paper copy of the repair manual but not on the CD ROM? If so is the paper copy available for this model/year (A4 / 1999)?

Any help anybody can give will be greatly appreciated!

Jim Harper
fast928

Posts: 4,192
Registered: 03/01/02
Re: A4 Wiring Harness Problem(?)
Posted: Aug 2, 2003 9:50 PM   in response to: jimharper in response to: jimharper
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Those positive connections are very hard to find. The harness location can be found on page 97-7. However, finding the harness doesn't give you much since the welded connection is not located at the harness.

Problems with these connections are very rare. In the early 80's there were some problems but those were corrected in the late 80's/early 90's and haven't re-appeared since. It is very unlikely that these connections are causing your problems.

You simply need to follow the procedure located on page 01-206. This is the code that is getting registered and this is what needs to be checked out. Test exactly as outlined for 01203.

According to 01203 (and other problems you describe) it looks like you have a problem with the (green) wire at terminal #10. Basically, you're going to want to make sure this wire is at fault and then trace this wire to it's fault.

If the wire always tests fine then you may want to look at the cluster or the ABS unit.

1) Don't think so.

2) Only the other post.

3) Yes, there is information from the instrument cluster that is needed for the ABS unit to work properly.

4) Not that I know of.

The HVAC problems could inidcate additional problems with the cluster. The cluster may have two strikes against it already!

Hope this helps!
Art

Posts: 2,743
Registered: 09/08/00
Re: A4 Wiring Harness Problem(?)
Posted: Aug 2, 2003 11:41 PM   in response to: jimharper in response to: jimharper
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Good Evening,

Just a point to remember regarding the ABS ECU (and several others).

With regards to the ABS warning light on the dash; it is the job of the ECU TO TURN THE LIGHT OFF if everything is OK, not turn it on if something is amiss. This may seem like a simple matter of semantics, but consider: how could the light come on to indicate a missing or unpowered ECU? If there is a fault, that "OK" signal to the warning light is removed which turns on the light. I would suspect a defective ECU which clutters the K wire giving you the "comm error" DTC.

So where am I going with this? Just this thought: look for things that cause the electrical power to the ABS ECU to be lost, interrupted, or degraded. That includes grounds. Unfortunately, you'll have to resort to using an Ohm meter and do some pin outs using the wiring diagrams. Andrew is correct with his thoughts; there is no more information.

Arthur LeBrun
Bentley Publishers
jimharper

Posts: 6
Registered: 12/09/03
Re: A4 Wiring Harness Problem(?)
Posted: Aug 3, 2003 7:50 PM   in response to: Art in response to: Art
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Thanks guys. I'll follow though with your ideas and post what I come up with.

Arthur, thanks. Your point makes infinite sense (if the ECU fails you want the alarm to light up). As to pin-outs, ohm meters and the like, not to worry. I grew up hands on in the manufacturing process control industry and have no problem continuity measuring, cutting, crimping and soldering nor do I with testing computer logic by playing with the signals going in and out of ECUs. I've learned to pray too. None of the above has helped so far in this case.

I've searched and searched on the web for a technical manual for the Bosch 5.3 controller that would tell me what the signal voltages are supposed to be on each line. The closest I came was the list at http://www.vectorbd.com/peugeot/bosch.html that indicates that there WAS a "Bosch online technical information" site that is "currently dead...."

Regarding the green wire Andrew mentions (the one on dwg 58/1) that goes from pin 10 of the ABS, though pin 9 of Orange connector T10b in the left A pillar connector station (which I have uncovered so I could check the connector) though mystery connection A91 (58d - by the way what does the '(58d)' on the drawing refer to?) and on to pin 11 on T32a, the green connector on the instrument cluster: Do you know what the signal level is supposed to be to turn OFF the ABS warning light - is it ground, +5v, +9v, +12v? (Sorry about the run on sentence) I thought that if I just cut the wire and fed it the "ABS OK - turn the light off" signal directly into the instrument cluster end of that wire, that would confirm whether that was indeed the problem. I just don't want to fry any electronics by putting the wrong voltage onto it.

Thanks,

Jim

jimharper

Posts: 6
Registered: 12/09/03
Re: A4 Wiring Harness Problem(?)
Posted: Aug 3, 2003 8:08 PM   in response to: jimharper in response to: jimharper
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Regarding signal levels, how about the "turn off the warning light" signal on the green/red wire from ABS pin 21 to pin 19 on T32 the blue connector on the instrument cluster (via T10b, pin 6). Isn't this the signal I should be able to toggle by grounding it or putting the right positive voltage on the wire to turn the warning light on / off?

Jim
fast928

Posts: 4,192
Registered: 03/01/02
Re: A4 Wiring Harness Problem(?)
Posted: Aug 3, 2003 10:31 PM   in response to: jimharper in response to: jimharper
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The signal wires are not given. Really the only test you can run is for continuity. If you check between these points this will test the wire.

To find out what the signal is you would have to find a working one to test. If possible it's best to swap in a known good unit.

I would rule out everything else first (wires, fuses, etc.) Then if everything pointed to the cluster I would begin to entertain ideas on testing that.

I don't see a 58d listed.
jimharper

Posts: 6
Registered: 12/09/03
Re: A4 Wiring Harness Problem(?)
Posted: Aug 18, 2003 12:52 AM   in response to: jimharper in response to: jimharper
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Problem resolved. I wanted to pass along how and thank you folks for your help.

It was indeed a failure internal to the Bosch 5.3 ABS unit. As this thread shows, I had tried a number of things, including removing the instrument cluster to test wire continutity based on the DTC code I was getting. Usually the ABS would not communicate with VAG-COM. One morning when I was about to give up, I turned on the power and voila the ABS was talking to VAG-COM. I could check DTC's, read values, etc. But when I tried the output tests, the first of which is to run the pump, the unit chattered and "went offline" again. The pump had not started. I tugged and pulled at the cables/connector to no avail. Then - don't laugh now - on a hunch I tried universal test method #1 - I tapped it with a hammer. It came back "on line." Same situation, when ever I tried to get the unit to actually DO something, it conked out. Every time I smacked it with the hammer, it came back.

The problem with VAG-COM being unable to communicate with the HVAC controller turned out to have nothing to do with the ABS problem. I contacted Uwe Ross, VAG-COM's developer, who told me that he had seen HVAC communications problems before and to change some settings in VAG-COM (per the FAQ on his website). Sure enough I did that and the HVAC unit started "talking" and checked out just fine.

Having confirmed that the ABS was dead, I got on the Web and found a salvage yard that had a used unit in good condition from the same vehicle model and year and features and ordered it.

Also while on the Web I found a phone number for something called the "Audi America Customer Advocate" and for the heck of it asked my wife to call them (it is her car). The guy who answered took the information but told her that she was out of warranty, there was no recall, etc., etc., etc. So I waited for the used unit to arrive. The next day, to my total surprise the phone rang and is was the Audi guy telling me to take the car back to the dealer where they would replace the ABS unit entirely at their expense.

I put the instrument cluster back in, put the trim back that I had removed and took the car in. Next day we had it back. It's been a week now and it is running fine. The dealer quote for this replacement, which was what set me to trying to do it myself - had been $1,500. Our cost was zero. Great way to keep a loyal customer, huh? We'll be back to buy another vehicle from Audi, no doubt, in the future.

The used ABS unit is going back in the morning.

Thanks guys again for the great help.

Jim
fast928

Posts: 4,192
Registered: 03/01/02
Re: A4 Wiring Harness Problem(?)
Posted: Aug 18, 2003 9:22 PM   in response to: jimharper in response to: jimharper
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Finally, a good Audi service story.

Thanks for the update. Glad you got it fixed!!
diatribe69

Posts: 33
Registered: 12/09/03
Re: A4 Wiring Harness Problem(?)
Posted: Sep 3, 2003 2:55 PM   in response to: jimharper in response to: jimharper
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From the various forums I've been reading, this problem is occurring on a lot of relatively new VW's and Audi's. An ABS module going bad just doesn't sound right.

In the 2 years I've had the car, I think my ABS has been activated once, maybe twice.

As far as bang for buck, that's a pretty s**tty service record from Bosch.

I am on the phone ASAP to VWofA to see if they're gonna cover the cost of possible replacement.

Jim, any other suggestions?
jimharper

Posts: 6
Registered: 12/09/03
Re: Bosch 5.3 ABS Failures
Posted: Sep 3, 2003 6:36 PM   in response to: diatribe69 in response to: diatribe69
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The way we got our Bosch 5.3 ABS unit replaced for free was by contacting these guys:

http://www.audiusa.com/customer_care_feedback/

When the "Customer Advocate" called back I had my wife talk to him, she being calmer than I. After the call she thought she had gotten the brush off because he said he had no information that there were excessive failures of the ABS but that he would 'call the dealer' (Stevens Creek Audi). Then lo and behold he calls back the next day -- I took this call -- and simply simply said "We will take care of it. Call so and so at the dealer."

This by the way is the same dealer who at the beginning of this saga told me that it would be $1500 to replace the "ABS pump" plus that we really really needed to have some engine seals replaced. With 53,000 miles on it, the seals are just fine, thank you very much. If Audi had not picked up the tab I was going to either do it myself or have these guys, who I think are good and honest, do it:

New Dimensions
2240 De La Cruz Blvd
Santa Clara, CA 95050
408-980-1691

The service manager there told me that they had just replaced the same unit for another Audi customer with similar mileage. He also told me, by the way, that the VW price was lower than the Audi price for the same exact part number and that he bought the other guy's unit from VW for that reason. His quote for our car was +/- $1,300 for the work, $1,000 of which was the ABS unit, the rest labor.

Hope this helps,

Jim
diatribe69

Posts: 33
Registered: 12/09/03
Re: Bosch 5.3 ABS Failures
Posted: Sep 4, 2003 2:12 PM   in response to: jimharper in response to: jimharper
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Yes, I am familiar with New Dimensions. They're a respectable shop.

I have an appointment at Stevens Creek VW on Monday to get a positive ID on what the problem is. My personal mechanic doesn't have the right software on his VAG (or VAG knockoff) to read the ABS codes. I have VAG-COM running on my laptop and I got code 01203, the same one you got when the ABS light goes solid and the BRAKE light starts flashing. I don't have the skill to go in and test voltages to see if it could be anything other than a faulty ABS module.

I have VWofA apprised of my appointment. Once the dealer diagnoses it and it turns out to be a faulty ABS module, I will call VWofA and they'll give me a resolution, which is hopefully as a positive as yours.

It just doesn't make any sense as to why an ABS module, something that is rarely, if ever, activated would go bad on a car with not too many miles. The fact that it costs so much just adds to my frustration.

Thanks for the info!
diatribe69

Posts: 33
Registered: 12/09/03
Re: Bosch 5.3 ABS Failures
Posted: Sep 8, 2003 6:18 PM   in response to: diatribe69 in response to: diatribe69
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Jim,

VWofA (Stevens Creek VW) is also covering my repair.

Sounds like a "silent recall" to me. I think they're covering all the units that come in before NHTSA requires them to do a complete recall. A lot cheaper to replace a few broken ones then to replace all broken or otherwise.

Thank goodness..the replacement module costs $1,087, plus 3 hours to replace.

Patrick
mkp007

Posts: 2
Registered: 12/09/03
Bosch 5.3 ABS unit - Audi and VW
Posted: Nov 1, 2003 4:02 PM   in response to: jimharper in response to: jimharper
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Jim,

Thanks for the great insight to this common problem. My car is the following:

Audi A4 1999 2.8L Quattro w/ Tiptronic 56,000 miles

I've noticed similar symptoms. ABS light comes on after about 10-15 min of driving (when started from cold). The brake light also comes on but is flashing (along with three loud annoying beeps). I took it to the Audi dealership (Hoehn in Carlsbad) and they told me the ABS unit needed to be replaced ($1000 for the part and $270 for labor, ouch!). I contacted a customer care representative and it doesn't sound like I'm going to be granted the same luck as many others reported in this forum (both VW and Audi owners).

As a first time Audi owner (I bought the car used with 48,000 miles) my optimistic perception has quickly diminished. Not only is the ABS module out but so is the Tiptronic switch. One visit to the doctor and the bill is up to 10% of what I paid for the vehicle.

I'm holding off on the repairs in hope of a cheaper solution. If Audi doesn't pick up the tab, I may resort to a used Bosch unit. How easy is it to replace? Please note I'm fairly handy but not an auto mechanic. Therefore I'm looking for "disconnect this plug, unbolt the unit, put the replacement unit in, reconnect the plug, and go" type solution. Will it be more difficult then this?

Thanks for any additional advice you may have on this.

Mark.
docurley

Posts: 25
Registered: 01/06/04
Re: A4 Wiring Harness Problem(?)
Posted: Dec 11, 2003 3:38 PM   in response to: jimharper in response to: jimharper
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Just read this topic after a link from socalaudi where I had the same problem. This information is great, I have a 97" 2.8 Quattro with the same code and warning lights. So imagine how pleased I am that someone went to all this trouble and posted this information, all I can say is thanks guys.
Now I'm goner try my luck with Audi UK and see if I get any luck.
docurley

Posts: 25
Registered: 01/06/04
Re: A4 Wiring Harness Problem(?)
Posted: Dec 15, 2003 12:30 PM   in response to: docurley in response to: docurley
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Well my Dealer wont have any of it they say my car is too old to justify have the ABS changed, so I have to find me a second hand unit.

After phoning around they all want the part number, which I will find tonight if I can find the ABS unit, anyway the cheapest quote is only 100 ($160) compared to 1200 ($1700) what a difference.
docurley

Posts: 25
Registered: 01/06/04
Re: A4 Wiring Harness Problem(?)
Posted: Dec 18, 2003 12:27 PM   in response to: jimharper in response to: jimharper
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Well after hunting through all the post on here (ok, not all but alot) i found this one.

Warning lights and ABS/ASR
Posted: Sep 20, 2003 5:46 PM Reply


Just realised why I can't find any wiring diagrams for my ABS system, my engine code (ABC) isn't covered by the Bentley manual cd I have!! HELP!?
I've already posted on this, see Frustrating warning light thread below.............
But now........ took car into Audi on Friday for new instrument cluster, was supposed to take 1 hour maximum,
they worked on it all day, I know because I was there too! Even with the new cluster fitted the warning lights still came on and numerous faults were still present, one of which was that they couldn't "talk" to the dash panel, I already knew I couldn't with VAG 1551, sooooooo........... a Master technician was assigned to find the fault, he eventually traced it to the ABS control module, when that was unplugged he could communicate with all systems, so their advice and diagnosis was a new ABS unit, approx 900!!! plus labor!
This morning I decided that I couldn't make it worse so had a tinker, there are 2 connectors to the ABS pump unit, 1 on the top, a big long one and after a rummage I found another 2 pin one underneath, I unplugged the 2 pin and cleaned it, re connected it and all seems ok now, I've road tested the car and the ABS and ASR both work perfectly, dunno what I did, but it worked!!
Can anyone tell me what the 2 pin connector is?
The pump is part number 8E0614111E ( I belive this a later pump?)
Hope someone can point me in the right direction here!
Thanks!

Message was edited by: UK_A4_Owner at Sep 21, 2003 6:13 AM

And so I'm goner try it tonight or at the weekend as the guy said it cant do anymore harm.

docurley

Posts: 25
Registered: 01/06/04
Re: A4 Wiring Harness Problem(?)
Posted: Dec 18, 2003 12:35 PM   in response to: jimharper in response to: jimharper
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Well after hunting through all the post on here (ok, not all but alot) i found this one.

Warning lights and ABS/ASR
Posted: Sep 20, 2003 5:46 PM Reply


Just realised why I can't find any wiring diagrams for my ABS system, my engine code (ABC) isn't covered by the Bentley manual cd I have!! HELP!?
I've already posted on this, see Frustrating warning light thread below.............
But now........ took car into Audi on Friday for new instrument cluster, was supposed to take 1 hour maximum,
they worked on it all day, I know because I was there too! Even with the new cluster fitted the warning lights still came on and numerous faults were still present, one of which was that they couldn't "talk" to the dash panel, I already knew I couldn't with VAG 1551, sooooooo........... a Master technician was assigned to find the fault, he eventually traced it to the ABS control module, when that was unplugged he could communicate with all systems, so their advice and diagnosis was a new ABS unit, approx 900!!! plus labor!
This morning I decided that I couldn't make it worse so had a tinker, there are 2 connectors to the ABS pump unit, 1 on the top, a big long one and after a rummage I found another 2 pin one underneath, I unplugged the 2 pin and cleaned it, re connected it and all seems ok now, I've road tested the car and the ABS and ASR both work perfectly, dunno what I did, but it worked!!
Can anyone tell me what the 2 pin connector is?
The pump is part number 8E0614111E ( I belive this a later pump?)
Hope someone can point me in the right direction here!
Thanks!

Message was edited by: UK_A4_Owner at Sep 21, 2003 6:13 AM


And so I'm goner try it tonight or at the weekend as the guy said it cant do anymore harm. oooops forgot to ask where is the dam module!!!

boxedin

Posts: 1
Registered: 11/19/04
Re: A4 Wiring Harness Problem(?)
Posted: Nov 19, 2004 7:06 PM   in response to: docurley in response to: docurley
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Docurly,
I just wanted to thank you, I have a 98 A4 and had the abs light code 01203,I had a "M" unit and I found a used "A" unit for $200.00 put it on like you said with the addition of the two new lines. Everything is fine now and I thank you for your detailed information.

Jack
docurley

Posts: 25
Registered: 01/06/04
Re: A4 Wiring Harness Problem(?)
Posted: Dec 24, 2004 7:33 AM   in response to: boxedin in response to: boxedin
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Well I'm glad to see this Thread has helped a few people as has said by others this is a common problem for our cars and Audi don't want to know.

It would be nice to here from other who have tried all the advise on this and see if it helped them to or if they have something to add.
Gee

Posts: 1
Registered: 08/24/05
Re: A4 ABS Control Unit Problem
Posted: Aug 24, 2005 2:18 PM   in response to: boxedin in response to: boxedin
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Hi guys,
i have been reading all your comments. i have the same problem but i have bought a rebuilt module and my mechanic has installed it but for some reason it keeps burning out. we have replaced the unit three times already under warrenty thank *** but it keeps happening, and im planning on selling the car and need to fix it. Is there any special thing u have to do to install it, we have been just replacing then unit. do we need to bleed the brakes or reset something? can anyone give me any help why the **** it keeps burning the units out? would really appreciate it. send me an email at gee_kostop@hotmail.com if u can help. thanks.

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