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  #1  
Old 12-04-2004, 09:26 PM
Hatterasguy's Avatar
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What trips the ABS light on a W126?

My ABS light has been coming on every so often for the past month. It is starting to happen more often now so I'm thinking I should try to fix it. What happens is that I will be driving and it will just come on, it doesn't matter if I am on the highway, around town, braking, or sitting in traffic. But as soon as I shut the car off and restart it the light will go away and not come back for a few days. Any ideas? A bad wheel sensor maybe? When I first changed the front brakes back in early May it came on for a mile and went off. I assumed I had got some junk on one of the sensors that came off.
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  #2  
Old 12-04-2004, 11:48 PM
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Me too again...

Hattie,

I seem to be following many of the same repairs as you. For the past 6 months I have had occasional abs lights on. Sometimes everytime I drive it, sometimes nothing for a week. I've recently had all 4 calipers, hoses, and master cylinder replaced. No difference. It does seem a little more frequent in the cold weather.

Another recent thread here ( or maybe in the technical forum) suggested checking the resistance of the front wheel sensors or the wiring going to them. They suggested there is a connection point on the passenger side in front of the battery. I haven't had a chance to look with work and the holidays. My next step is to find the connectors and wait for the light to come on, then measure the resistance to see if it differs.

Let me know if you find other items to check.

Chuck
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  #3  
Old 12-05-2004, 12:38 AM
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If the ABS system detects a bad signal or an imbalance, the light will turn on. Clean the ABS sensors in the front wheels and the toothed wheels, reluctors I think, and any rear sensors, I can't recall if the car has 3 or 4 channel sensors. The brakes pads have metal bits and the rotors wear so there are fine metal filings attached to the sensor. That can cause a bad signal.

Have you been able to read any codes.
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Currently 1965 220Sb, 2002 FORD Crown Vic Police Interceptor

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  #4  
Old 12-05-2004, 07:12 PM
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You can read codes off these cars? I thought they were to old.

I cleaned the front sensors out when I did the front brakes. Maybe I wil just live with it until it warms up. I don't feel like taking off the discs when it is 30 degrees out.
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2005 Chevy Silverado, white on black.

"No free man shall ever be debarred the use of arms. The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government."
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  #5  
Old 12-05-2004, 10:26 PM
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Mine did the same thing. It turned out to be the ground wire on the battery terminal was loose. If I am not wrong, the RPM needle was flickering as well at the time, which would indicate low voltage.

Another time it did it and the alternator had to be replaced.

Goof luck.
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  #6  
Old 12-06-2004, 11:46 AM
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No the tach needle seems to stay pretty constant. But thanks for the heads up I will check the ground and keep and eye on the needle next time the light comes on.
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2005 Chevy Silverado, white on black.

"No free man shall ever be debarred the use of arms. The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government."
-Thomas Jefferson
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  #7  
Old 12-06-2004, 12:08 PM
Benster Tom
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I notice that my Anti-Lock light does that from time to time. Coming on and sometimes it doesn't. Also I've noticed from time to time that at a stop light my "speedometer needle" goes up and down alot. Then of course it's okay once I start to move.
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  #8  
Old 12-06-2004, 02:24 PM
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Talking

Hatterasguy,
I had that problem on my 85 300SD. I used to do it once I started rolling in the morning, and would nto shut off until I turned off the car and then when I would turn it back on again, light was off again until I started to move it. Funny thing was it never shut off until I shut off the car. So, I got underneath the car and from the side facing the engine, I found the sensors. They are attatched with allen screws. I took them out, and you would not beleive how much metal shaving where attatched to it like a magnet. I cleaned it out and I cleaned out the hole it was in (found more shaving inside). Did both wheels just in case. Put the sensors back in there, lo and behold, no more light. I would take those sensors our, clean them out and replace them. In my case it took me 20 minutes to do it. Note that I had recently repalced both brake pades and pad senors in the front. I also replaces those wheel sensors and replaced brake pads and calipers in the rear. Now mine only has one sensor in the back mounted on the differential. But I am almost certain yours has sensors on all 4 wheels. It really is a very simple job, and you'll notice a difference in the pedal pressure once they are working correctly. In Florida ABS is not a luxury item.. With as many people we have on the roads (that should not be on the roads!) Sudden stops are all too frequent. Good luck!!!
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  #9  
Old 01-09-2005, 02:46 PM
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one step further....

Folks,

Still having intermittent ABS light sightings. More in the cold, less when warmer. I did pull the sensors out of the backing plates yesterday. There was a little grease on one. I washed them off with brake cleaner. I also sprayed cleaner in the sensor hole and turned the rotors. A little bit of stuff came out but not much. I went for a ride last night and the light came on again... RATS!

I found the connectors from the sensors. The driver's side is near the master cylinder. The passenger side is in front of the washer fluid tank. Both sensors measured as "opens". Does this sound right? I checked on fastlane and they go for about $150 each, so this isn't really a replace and try it unless I'm more sure.

I think the next step ( depending if anyone has an answer on the resistance question) is to actually take off the rotors and clean them.

Other suggestions? I did not try to check the rear sensor yet, I suppose that could be the culprit here as well.

Chuck
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  #10  
Old 01-09-2005, 04:20 PM
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Quote:
Originally Posted by CSchmidt
Folks,

Still having intermittent ABS light sightings. More in the cold, less when warmer. I did pull the sensors out of the backing plates yesterday. There was a little grease on one. I washed them off with brake cleaner. I also sprayed cleaner in the sensor hole and turned the rotors. A little bit of stuff came out but not much. I went for a ride last night and the light came on again... RATS!

I found the connectors from the sensors. The driver's side is near the master cylinder. The passenger side is in front of the washer fluid tank. Both sensors measured as "opens". Does this sound right? I checked on fastlane and they go for about $150 each, so this isn't really a replace and try it unless I'm more sure.

I think the next step ( depending if anyone has an answer on the resistance question) is to actually take off the rotors and clean them.

Other suggestions? I did not try to check the rear sensor yet, I suppose that could be the culprit here as well.

Chuck
CSchmidt,
Before going into any conclusion you MUST do the rear wheels also. MB ABS systems are awesome and very very precise. If there is one false reading the system shuts itself off and thats when you get the light. In your case (SDL) you should have sensors on all four wheels. Unlike mine that has a sensor on the differential. Do the very same thing you did to the front ones and then lets go from there!! Good luck!
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  #11  
Old 01-09-2005, 07:16 PM
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My ABS light seems to have heeled itself! When it warms up this spring I will fix it, ABS is nice but I can live without it. I drove my Camry for almost two years and it didn't have ABS.
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2005 Chevy Silverado, white on black.

"No free man shall ever be debarred the use of arms. The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government."
-Thomas Jefferson
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  #12  
Old 01-09-2005, 11:46 PM
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hattie, we had the same problem with my dad's 300E. next time you have the rotors off, clean the teeth and the sensors off then enjoy your ABS. Personally, it drives me nuts to see a light on the instrument cluster on. When I bought my "new" SDL, the brake light came on the next day. The parking brake pedal wasn't quite sprinnging back just enough to flip the switch off so I have an inconspicuous wire holding it up. You can't see the wire unless you crawl under the dash. Then, two days later, the "light out" light came on and I replaced the license plate bulb. I didn't think one of those lights could trip the light on.
Thanks
David
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  #13  
Old 01-09-2005, 11:54 PM
VeeDubTDI
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My ABS would turn on periodically for a couple of months before it started coming on every time I start moving, like it does now. It would usually come on when the right front wheel hit a bump in the road; even small seams and highway transitions could do it. It turns out that the right front wheel speed sensor's wire had torn out of it's 90 angle boot. I haven't investigated further into the repair process because I work in a black hole that sucks up all of my time... this is my third 14-hour day in a row, one more tomorrow.

In the beginning, the light would turn back off if the wire made another connection to the sensor.

Good night to all of my fellow ABS-less drivers.

Last edited by VeeDubTDI; 01-09-2005 at 11:59 PM.
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  #14  
Old 01-10-2005, 10:05 PM
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cleaning experiment - day 1

Folks,

I had an hour yesterday, the weather was nice, and the family was out shopping - time to play! I looked around and pulled the rear sensor. Only 1 on my car attached to the differential. It was clean and had a different shape than the front sensors. The tip of the rear was like a small blade screwdriver. Put it back in after I wiped it off.

Removed each front again. This can be done easily with the wheel on and jacked up. While the first sensor was out I noticed with a bit of crawling under the car you can see the teeth of the rotor from the sensor hole. I spent 10 minutes on each wheel rotating it slowly and spraying brake cleaner to get any junk out of the teeth. There was very minor dirt/stuff only, but I cleaned them thoroughly. It looked like there was some grease filling the cavity between some of the teeth, but no major accumulations of brake dust or filings. BTW - the front sensors had a U shaped end. Did the other side as well.

After a repair, I usually wait 3 or 4 days to confirm my results, but thought in this case some of the info here could be useful. After 1 day with several trips and about 100 miles of driving - no ABS lights. It was warm which seems to mitigate the problem... so I'll let you know this weekend when the cold is supposed to return. The brakes also felt different. Previously, at many slow stops - like inching up to the garage - I would get what I think is the ABS system vibrating as the brake pedal was pushed. Not today, a much different pedal feel. More solid and linear.

My fingers are appropriately crossed. I post the news later if the problem reappears. Good luck to all on this.

Chuck
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  #15  
Old 01-10-2005, 10:45 PM
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check the Over Voltage Protection relay and it's fuse... fixed my ABS light always coming on.
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Old 01-10-2005, 10:45 PM
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