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ASC and ABS lights E39
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jteplitz



Joined: 22 Apr 2002
Posts: 38
Location: Pittsburgh and NY

PostPosted: Sun Oct 12, 2003 4:02 pm    Post subject: ASC and ABS lights E39 Reply with quote

My 99 528i had some electical gremlins a while back - the ABS and ASC lights would come on and the radio would go off. I replaced the battery and it seemed to fix the problem.

Last night, when I got into the car, both lights stayed on. This morning, it didn't happen, but this afternoon, it did. Hitting the ASC switch doesn't matter, and I accelerated and braked hard to see if the systems were working. Both ASC and ABS were not working.

Anybody else with this problem? Anybody know the cause?
Thanks!
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Jaideep



Joined: 09 Oct 2003
Posts: 22
Location: Roanoke, VA

PostPosted: Mon Oct 13, 2003 2:36 pm    Post subject: ASC and ABS lights E39 Reply with quote

My 1998 528i has very similar problems. In my case, the the ABS light comes ON, the radio cuts off, and the cruise control cuts off. The problem fixes itself within a day or two. The dealer has no explaination.

One thing I noted that this happens inevitabily on wet days! Call it a coincidence, but I suspect high moisture in the air is somehow connected.
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edjack



Joined: 04 Feb 2002
Posts: 3887
Location: San Jose, CA

PostPosted: Mon Oct 13, 2003 8:32 pm    Post subject: ASC and ABS lights E39 Reply with quote

Might be a bad speed sensor on the left rear wheel.
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jteplitz



Joined: 22 Apr 2002
Posts: 38
Location: Pittsburgh and NY

PostPosted: Wed Oct 15, 2003 1:03 am    Post subject: ASC and ABS lights E39 Reply with quote

Wow, now that's intriguing! I wondered about speed sensors, but how do you know which wheel?
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BrandXYZ



Joined: 10 Aug 2005
Posts: 1
Location: Santa Maria, Ca.

PostPosted: Wed Aug 10, 2005 9:29 am    Post subject: ASC and ABS lights E39 Reply with quote

Had the same problem, with other complications; Cruise control, speedo and odometer not working. Had BMW run the diags and the problem was a defective ABS controller unit. Got a second opinion, and the results were the same. Replaced the controller; Cost: $900.00
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SPL



Joined: 26 Jun 2001
Posts: 10
Location: Dieppe, N.B., Canada

PostPosted: Thu Dec 01, 2005 11:20 am    Post subject: Reply with quote

i think you have 2 different problems. The ABS thing is well documented in this forum. The radio sutting off etc is another unrelated problem. I was having some weird electrical problems and it turned out to be a bad ignition swith. It was explained to me that when you turn on the ignition, lots of systems in the car self test and if the systems get a bad signal through the ignition switch, it can cause all kinds of odd behavior. When i changed my ignotion switch, all my weird electrical glitches went away (cruise, radio etc ... ). Now i only have my ABS problem remaining. I hope this helps you.
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*-jester-*



Joined: 29 Jan 2004
Posts: 13
Location: East yorkshire. UK

PostPosted: Thu Jan 26, 2006 5:55 am    Post subject: Reply with quote

I am also experiancing the ABS ASC lights but mine usually comes on when I drive over a bump in the road (drain cover for example.) but it does not happen all of the time!
Sometimes I can travel 80 miles before the lights come on, sometimes I can't even drive for a mile before the warning lights come on!

I've read elswhere on this forum that if it also effects the cruse control too then it's probably the left rear speed sensor that's faulty.
...However, my cruse control still works fine when the ABS lights are on so can I assume that it's not the left rear sensor??

...great 1 down 3 more sensors to check/replace!
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alanfp



Joined: 07 Feb 2002
Posts: 461
Location: UK

PostPosted: Thu Jan 26, 2006 6:22 am    Post subject: Reply with quote

So, Jester, does the ASC light tend to come on when you drive over a drain cover on wet days rather than dry????? Must be electrical then Laughing
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*-jester-*



Joined: 29 Jan 2004
Posts: 13
Location: East yorkshire. UK

PostPosted: Thu Jan 26, 2006 6:34 am    Post subject: Reply with quote

Yeah alanfp it's more susceptible to occure in the wet but it definatly still happens when it's dry too! Confused
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edjack



Joined: 04 Feb 2002
Posts: 3887
Location: San Jose, CA

PostPosted: Thu Jan 26, 2006 3:41 pm    Post subject: Reply with quote

Gleaned this from the roadfly forum. May help:

Car: 97 540i

Symptoms: Dreaded yellow triangle, ABS light, and CEL on. All other functions (speedo, tach, cruise control, trip computer, etc) working.

Procedure: Pull the ABS controller out and disconnect it from the wiring harness. Mine is under a panel to the left of the glove compartment. Remove the wiring backshell so you can get at the wiring connections on the back side of the connecting plug (you need to be able to see the colors of the wires and get a Ohm meter probe on them).

Using a Bentleys Electrical Manual find the connection diagram for the wheel sensors to the ABS Controller. The pin designators will most likely be wrong (they were for mine) BUT the color designators for each of the wires is correct.

Example: Right Rear sensor is connected by two wires, one blue and one blue green.

Connect Ohm meter across these two pins. NOTE: I wound paper clips around the probes to make a very small probe tip which helps. Write down the resistance reading. Mine was 3.08k ohms.

Work through the other 3 wheels and write down the resistance readings. If any of the pairs is open (i.e. infinite resistance) you have a bad connection between the ABS Controller and the wheel sensor. You can then remove the affected wheel, unplug the sensor, short out the pins on the plug (not the wheel sensor part but the chassis wiring part) and if the ohm meter is still reading open you have a broken cable between the wheel sensor and the ABS controller. If the cable is good connect the ohm meter across the wheel sensor itself and if the cable still reads open you have a bad wheel sensor, replace and retest.

Here is what I found. All wheels read 3.08k ohms except the right rear which read 4.4M ohms. This sensor was replaced during my rebuild exercise and it looks like they provided the wrong part. I replaced the part with a dealer item and retested. 3.08k ohms was read with the new part. Reconnected everything and the ABS light went out, the yellow triangle light went out. I used my OBDII computer interface to clear the CEL light and all is well again.

Total testing/repair time: 2hrs and 35 minutes!

Here is my theory. The "older" ABS Controllers (like mine) use sensors with the lower reisitance (3.08k ohm) while the newer Controllers use the higher resistance sensors (4.4M ohm). The part I bought was from a 02 E39! I can return it but I think I will use it to test my 00 528 problems first Smile .

Hope that helps others with similar problems

Scott

Update

Posted this earlier with a "theory" at the end that I have since disproven and discovered a real tip for those troubleshooting speed sensors.

If you use the ohm meter on the wheel sensors (as described below) and you get a reading of 4.4M Ohms that speed sensor is BAD. I verified on my 00 528 this weekend. The procedure works great so far on both the 97 540 and the 00 528.

NOTE: The normal resistance readings for the old style ABS computer (mounted beside glove box inside) is 3.0k ohms. The normal resistance readings on the newer ABS computer is around 8.0M ohms.

Hope this helps!

Scott

Also, here is a place to get you ABS unit repaired, rather than replaced. Roadfly members who've done it give them good marks.

http://www.modulemaster.com/
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Ed BMW CCA member since 1987 (Nr. 62319).
'97 540i 6 speed Aspensilber over Aubergine interior.
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*-jester-*



Joined: 29 Jan 2004
Posts: 13
Location: East yorkshire. UK

PostPosted: Fri Jan 27, 2006 3:13 am    Post subject: Reply with quote

I'm sure that will be a great help Scott, my car is a 1998 so my sensors should read 3.08k ohm too.

I'm going to have a go at the weekend while I'm fitting my new brakes, I'll post how it goes.

Cheers mate Smile
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John Vollenweider



Joined: 02 Mar 2006
Posts: 52

PostPosted: Sun Mar 05, 2006 7:20 am    Post subject: Reply with quote

Hi, My ASC light is also on, Air bag light came on when I hit a bump one day, has been on ever since. My new glitch is the horn, radio control and everything else on my steering wheel except heater button is INOP. I cannot turn cruise control on with button on dash either. I kinda suspected bad ignition switch since my radio at times is inop when I first put key in ignition and start vehicle. If I take key out and insert again radio comes on after 2,3 or more trys. Sometimes radio will go out while driving also, but it happened so rare that I didn't worry about it. Now it seems to be getting more frequent.

Thanks, John
You can see my POST from 3/4/06
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Steve Lewis



Joined: 29 Nov 2004
Posts: 4
Location: Columbus, GA

PostPosted: Mon Mar 06, 2006 8:23 pm    Post subject: ASC Fault Light Reply with quote

Great discussion on this topic, everyone. My '99 528i with 79K miles had the ASC triangle show up a few days ago. Associated with the fault light, the speedo, mileage gage and odometers went inop, and the ABS light came on. No other faults exist. I took the car to the dealer today for diagnostics. The dealer said the ASC module ("hard fault") and left rear speed sensor needed replaced. $913 and $143 for the parts, respectively. Based on what I have read here, I see no options but to replace the parts with new. Is there a more favorable alternative?

Thanks.

Steve
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edjack



Joined: 04 Feb 2002
Posts: 3887
Location: San Jose, CA

PostPosted: Mon Mar 06, 2006 10:26 pm    Post subject: Reply with quote

Yes, read my post of Feb 3, above, where I list a company that repairs the ABS electronics.
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Ed BMW CCA member since 1987 (Nr. 62319).
'97 540i 6 speed Aspensilber over Aubergine interior.
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Steve Lewis



Joined: 29 Nov 2004
Posts: 4
Location: Columbus, GA

PostPosted: Tue Mar 21, 2006 7:25 pm    Post subject: Reply with quote

I sent my ASC module to Module Master (ref. earlier post); $300 flat rate, 2-day turn, 5-year warranty. Received and installed the unit this evening, and the fault was gone. I highly recommend these folks (http://modulemaster.com/) for the repair. They were available by phone, kept my apraised of the status, and returned the unit professionally packaged.

Steve
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