Tomorow I will get a new ABS front left sensor (comes with a lot of wire harness ... together with brake pad wear sensor harness) and I want to replace it on my own. ABS and ASR lights came on occasionally. The mechanic's tester showed fault code "signal from left front ABS sensor". Sometimes when we rotated the wheel the tester did not show any speed, and sometimes we did not rotate it when the tester showed low speed (later I thought that mechanic's bluetooth earphones was maybe a reason for that, especially because the sensor's wire insulation is 16 years old).
Please comment all these facts.
1) i just wonder why my speedo was functional when ABS and ASR lights were on?
2) can somebody write a few words about replacing the sensor ... is there any useful tip? Or is it completely an easy job, which I assume it is?
yes i would agree. that's what most probably killed it when my mechanic replaced sway bar links (arms?).:crybaby2: Of course i cannot be sure, he is a very good mechanic and accidents happen ...
I replaced the sensor and its wire harness. An easy job 1 in scale from 1 to 10. Hard to believe but the connector for brake pad wear had only one metal contact. The other one was under the black plastic which I had to remove with a small screwdriver. At the end the connector showed up but it also felt appart. I had to made an improvisation. Fortunately the base of the pin which felt appart is made of metal and I screwed a screw into it and I shaped a stem of the screw into cylindrical shape to improvise a shape of the pin. Unbelievable. The price for a new sensor was 450 EUR. I did not want to bring the defected part back to the dealer, because I think the solution (a new pin) is stronger than original one. Actually I used dental technique; the new pin is made like a base for an artificial tooth. In addition, once the connector from the brake pad is in its place, nothing can happen to the pin, there is no forces which would act on it, etc.
After replacement I deleted fault code (signal from front left ABS sensor) and I started the car. Both ABS and ASR lights were on immediately, so situation was even worse then before (both lights came on at low speed). I turned the steering wheel to both ends twice and restart the car. The lights did not show up from that moment on. So far so good.
The black plastic tip on the pad sensor cable is supposed to be there. Sounds like it was missing from the other wire. You DO NOT want to use a screw or other hard metal pin for the purpose. The pad sensor is just a piece of soft copper wire in a plastic pin which holds it in the pad. As the pad wears the SINGLE wire contacts the brake rotor (which is at ground potential) and completes the circuit to the computer. Nothing fancy. As the pad continues to wear the soft wire is ground away no problem. But if you put a steel screw or pin in there it could damage the rotor (score it) or the pad.
As for an impact gun damaging the sensor, I believe that is just a rumor. The sensor is not a solid state device like a Hall sensor. It is just a coil of wire encapsulated in a metal shell. It is the same thing as the sensor on the flywheel. No vibration short of smashing it with a hammer could damage it.
The test was showing a very low speed when the wheel was not moving because there was an intermittent open circuit in the sensor cable. The conductor was broken inside the insulation and making and breaking contact over and over just sitting there. This broken cable is the problem. After 290,000km of bending and twisting every time the wheels are turned or go over bumps the cable just wore out. The sensor is still good. On my 500SEL I made REPLACEABLE wire harnesses with high quality cable and mini DIN connectors. So the next time the cable breaks I only have to rewire several feet of cable from the rotor assembly to the chassis and leave the sensors alone.
Thanks for the post. I am having the exact same problem. Did you take any pictures of fixing the wire? Can you give me more details on what replacement cables you used as well as more detail on how you replaced them.
The black plastic tip on the pad sensor cable is supposed to be there. Sounds like it was missing from the other wire. You DO NOT want to use a screw or other hard metal pin for the purpose. The pad sensor is just a piece of soft copper wire in a plastic pin which holds it in the pad. As the pad wears the SINGLE wire contacts the brake rotor (which is at ground potential) and completes the circuit to the computer. Nothing fancy. As the pad continues to wear the soft wire is ground away no problem. But if you put a steel screw or pin in there it could damage the rotor (score it) or the pad.
I can see that you know what you are talking about, so I think the situation is not clear because I used words instead of one picture. As a mechanical engineer I know that one picture tells more than 1,000 words. Please believe me that the original part 140 540 12 09 was faulted and I had to make a contact pin which was missing. I did not touch the pads or things which are parts of brake system on a car. I just made a new contact pin on a pad-wear connector which is part of ABS sensor+ harness. the reference was the old part and I just made a copy of it. So I was in a situation when the new part was not the same as the old part and I was not able to push one of the two pad's female connenctor into the male connector on a new part no. 140 540 12 09. Let's forget this because I am too lazy to make a picture ... I just think we did not understand each other . i wrote that information only to be informative for somebody who will have the same problem in the future maybe. That was the first time that I purchased defected MB original part. once again, I was not "clever too much" and i did not modify anything on a car. I just repaired broken pad-wear male connector which was evidently a result of a mistake during manufacturing. because the solution was even more stronger pin, I am happy with it.
As for an impact gun damaging the sensor, I believe that is just a rumor. The sensor is not a solid state device like a Hall sensor. It is just a coil of wire encapsulated in a metal shell. It is the same thing as the sensor on the flywheel. No vibration short of smashing it with a hammer could damage it.
This sounds great. So I do not have to worry on Monday when the mechanic will replace my both lower control arm joints? or should I tell him to remove the sensor first? I am afraid a bit ..
The test was showing a very low speed when the wheel was not moving because there was an intermittent open circuit in the sensor cable. The conductor was broken inside the insulation and making and breaking contact over and over just sitting there. This broken cable is the problem. After 290,000km of bending and twisting every time the wheels are turned or go over bumps the cable just wore out. The sensor is still good. On my 500SEL I made REPLACEABLE wire harnesses with high quality cable and mini DIN connectors. So the next time the cable breaks I only have to rewire several feet of cable from the rotor assembly to the chassis and leave the sensors alone.
I spoke with 2 mechanics and both said that the only good solution is a new sensor + harness. I learnt that many times there is no sense in improvisation, however if the problem will repeat on other wheels I will seriously consider your idea. So I need a cable with 4 wires is that right? and 8 connectors ... and something to hide (seal) those connectors on both sides ? my mechanic told me that such solutions are ok for about one week, so evidently people had tried this without a success.
A good news is that crusie control now works really smooth which was not a case before. First I renewed ETA and the smoothness jumped from 6 to 9 (scale 1 to 10). After left front ABS sensor replacement smoothness jumped from 9 to 9,9.
Can anyone suggest a place where I can order both front ABS wheel speed sensors (with cables)? I am in Canada but with the wonders of the internet and phone can order from pritty much anywhere. I contacted my local MB dealership and they have quoted me a very hefty price for these cables.
im i right onthe wheels there are a brake pad wear wire . and a abs wire rights and does the brake pad wear wire have any thing to do with ABS light comin on and and the wires change i hve a 94 and 95s wires are diffnt so i had to cut and twist the wires and placed tape on it will the wire still be good
I really need some help on this issue. I have a Mercedes w211 e320cdi 2004.
I had replaced the front passenger side suspension arm, and after that the car has come up with ABS and ESP error.
I took the car for wheel balancing, and tracking. Still the same problem.
I have taken the car to a local garage and had it connected to STAR Computer and it came up with rear drive side wheel sensor. The mechanic has checked the sensor, all ok but he said the voltage is not being delivered back to the sensor hence it is showing up an error. He has checked every thing on the car but still can not find the fault.
I have noticed if I leave my car for three days it loses the battery power may be its weak, but will that cause this issue.
Help is needed. Thank you.
Harry
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