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1993 400 SEL, 1985 308 Ferrari, 2006 F250 6.0, 2009 BMW X6
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8 Posts
Discussion Starter · #1 ·
My ABS light is on and my speedometer doesn't work. I disconnected my ABS/Speed sensor head at the wheel and it had trash around the head. While cleaning that off I noticed it had a strong magnetic pull to it. What all can I check before replacing the harness?
 

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W140 Mercedes 500 SE, 1992, European, 440.000 km
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3,959 Posts
first you must check error codes. there are 4 ABS sensors on the car. then you must repair/replace the sensor which is damaged or ruined.

As far as I know (but you must verify) the sensor comes with the harness and the price is about 300 - 450 EUR here in europe. there are some reports about repairing harness but this is not recommended of course.
 

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1993 400 SEL, 1985 308 Ferrari, 2006 F250 6.0, 2009 BMW X6
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8 Posts
Discussion Starter · #3 ·
Lucky me? I have only 2 ABS sensors One on left front one on right front. I do have 8 brake sensors 2 on each wheel, but only 2 ABS sensors. Remember this is a 1993 400 SEL. It does not have traction control.
 

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W140 Mercedes 500 SE, 1992, European, 440.000 km
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well I am not an expert for MB cars, taht's true. I just presumed that your car like mine has 4 ABS sensors. if somebody would ask me how many sensors each car in the world with ABS has, I would say 4 :). So you did not convince me but somebody else will probably confirm your statement. Sorry for now. anyway, two is more than one, so you have to check which one is bad.

in addition, I must also admit that i do not differ between the brake sensor and abs sensor. Another thing which somebody can explain here.
 

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1993 400 SEL, 1985 308 Ferrari, 2006 F250 6.0, 2009 BMW X6
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8 Posts
Discussion Starter · #5 ·
samosali, thanks for trying to help me. I said 8 brake sensors when I should have said 8 brake pad wear sensors. I bought the car new in 1993 and my wife still loves it even thou I have bought her 2 new BMW's since. She just likes the car. I guess I'll have to buy some scanner software if we are going to keep it (which we are) Only has 103,000 mi on it.
 

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W140 Mercedes 500 SE, 1992, European, 440.000 km
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you are welcome. Ok, now it is clear. 8 pad sensors makes sense. I still think that your car has 4 ABS sensors, but like I said, i am not an expert for MB neither for cars in general. for me it is logical that all 4 wheels are controled by ABS computer. What is the purpose of not to block only the front pair of wheels if the rear pair is blocked and therefore causing all negative effects? But like I said, I cannot be 100% sure because cars are not my speciality.

in my car the rear ABS sensors are not so evident like the front ones.

maybe you have built-in error codes device? I read that some US models have a blinker code reader under the hood near the computers box (right side at the windshield). if not, the only way is to somehow read the codes at the mechanic's and he will tell you which sensors are bad.

best regards.
 

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No software required, just build the code reader and read the codes on the 38 pin diagnostic connector. Lots of info in the archives.
 

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W140 Mercedes 500 SE, 1992, European, 440.000 km
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No software required, just build the code reader and read the codes on the 38 pin diagnostic connector. Lots of info in the archives.
that's true. you can make your own code reader for several dollars, just search this forum for solutions (type "error codes", "code reader" , etc.). If you need specific help let us know. I made it and it works fine. it is very very easy.
 

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1993 300E 3.2L non/4matic Chassis: 124.032 Engine:129.942
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My suggestion is to change the Overload Protection Relay and your ABS problem should be solved, I had the ABS light on my 93 300E so at first, I changed the ABS Relay in the unit itself and that didn't cure my problem, then I changed the OVP and my ABS problem including my Cruise Control issues were solved. The Relay was about $40 so its not a bad choice to replace it if its Origional, Best of luck, I hope I was able to solve your problem. The relay should be behind your battery under the plastic, attached to the right side of the ECU, it has a white top with a 15amp fuse in it.
 

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1996 S600 1991 560SEL 1995 S500 2009 S550
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My suggestion is to change the Overload Protection Relay and your ABS problem should be solved, I had the ABS light on my 93 300E so at first, I changed the ABS Relay in the unit itself and that didn't cure my problem, then I changed the OVP and my ABS problem including my Cruise Control issues were solved. The Relay was about $40 so its not a bad choice to replace it if its Origional, Best of luck, I hope I was able to solve your problem. The relay should be behind your battery under the plastic, attached to the right side of the ECU, it has a white top with a 15amp fuse in it.
Well said and the most prudent way to do before changing the sensors.

Samosali you are right there are 4 ABS sensors on 140's
 

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1993 400 SEL, 1985 308 Ferrari, 2006 F250 6.0, 2009 BMW X6
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Discussion Starter · #12 ·
Is the 300E the same as the 400sel the battery is in the trunk, so the relay is in the same place? My car is 100 miles away right now and I can't check it so I am asking. Also am very curious about rear abs sensors. The only thing connected to my rear hubs are Brake wear sensors and hydraulic brake lines. I bought the car new so nothing has been taken off. Could it be located somewhere else on the rear. The 400sel does not have traction control the 600 and 500 did.
 

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Zotye Auto 1.5T T600 2016
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52,804 Posts
My ABS light is on and my speedometer doesn't work. I disconnected my ABS/Speed sensor head at the wheel and it had trash around the head. While cleaning that off I noticed it had a strong magnetic pull to it. What all can I check before replacing the harness?
Front drivers side wheel speed sensor is used for both ABS and speedometer, does this help?
 

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Outstanding Contributor - Always Remembered, RIP
Zotye Auto 1.5T T600 2016
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52,804 Posts
Well said and the most prudent way to do before changing the sensors.

Samosali you are right there are 4 ABS sensors on 140's
Correct and each one has extra assignments besides wheel speed. The front left or drivers side is also allocated to the speedometer so you have your answer.;)
 

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1993 400 SEL, 1985 308 Ferrari, 2006 F250 6.0, 2009 BMW X6
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Discussion Starter · #15 ·
Thanks for the reply and the location of the one that controls the speedometer.
Thanks to all who replied. I will be needing more help as the car ages.
 

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1993 300E 3.2L non/4matic Chassis: 124.032 Engine:129.942
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Is the 300E the same as the 400sel the battery is in the trunk, so the relay is in the same place? My car is 100 miles away right now and I can't check it so I am asking. Also am very curious about rear abs sensors. The only thing connected to my rear hubs are Brake wear sensors and hydraulic brake lines. I bought the car new so nothing has been taken off. Could it be located somewhere else on the rear. The 400sel does not have traction control the 600 and 500 did.
I was doing some research and your 400 SEL doesn't seem to have the OVP, it wouldn't hurt to see if the Relays in the ABS unit are working, they are cheap, just make sure you have the part numbers off them.
 
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