Underlying problem leading to failure of front wheel speed ABS sensor

Herve'

New member
In the last two days, the left front wheel speed ABS sensor of my Leisure Travel Sprinter 3500 van has failed twice. Every time, just seconds before I got the ESP, ABS and Visit Workshop dashboard messages with the wheel skidding icon, I felt something snap around the front left wheel followed by a brief loss of power until the dashboard messages showed up. I read a number of posts and cannot relate my driving conditions to these of other sprinter owners with the same problem. No strong wind, the sprinter battery had been working fine, the cruise control was not being used, etc... I replaced both front wheel speed ABS sensor with Mercedes Benz ABS sensors after a MB certified mechanic scanned the car for the code of the failing component and was able to drive about 120 miles in good weather at good steady speed before one of the new ABS speed sensor failed again. Does this sound familiar? Any idea? I am leaving the Florida Keys in a few days with the Sprinter and its failed sensor and hope to make it (carefully) to Hollywood, FL, where I last replaced the wheel speed ABS sensors. I am looking for the underlying cause if the sensor failure. I am assuming it is not dirt and grit in the wheel well since the weather was great and the road conditions excellent.
 

hoosierrun

Active member
Do you know if the sensor has completely failed... or did it just set a code? Late last year I had a right rear sensor that kept throwing codes, even after it was replaced. After over an hour of troubleshooting by a dealer tech, they found chaffed wire (insulation just worn through) intermittently making contact with a metal bracket or brace. They were able to tape that up but unfortunately I also had a burned out ABS module. Total costs were near $1800 but fortunately I had an extended warranty.

Things to consider are a rubbing chaffed wire, bad connector/plug in the wire harness, or the module that processes the pulses. There may also be problem with the magnetic pickup or tone wheel (not sure of the technology used on this vehicle).
 

Herve'

New member
Do you know if the sensor has completely failed... or did it just set a code? Late last year I had a right rear sensor that kept throwing codes, even after it was replaced. After over an hour of troubleshooting by a dealer tech, they found chaffed wire (insulation just worn through) intermittently making contact with a metal bracket or brace. They were able to tape that up but unfortunately I also had a burned out ABS module. Total costs were near $1800 but fortunately I had an extended warranty.

Things to consider are a rubbing chaffed wire, bad connector/plug in the wire harness, or the module that processes the pulses. There may also be problem with the magnetic pickup or tone wheel (not sure of the technology used on this vehicle).
According to the mechanic the first sensor did not completely fail. There was intermittent contact...However, the second one was brand-new and should not be chaffed. I will share with mechanic and see what they have to say. Thank you!
 

Herve'

New member
Was the sensor physically damaged? Any sings of damage to the wire/harness? Its possible you picked up some debris with your tire, and it caught the harness.
I kept the failed sensor and it does not look physically damaged. I can see why the old one could fail after driving for a while (21000 miles) under less than optimum conditions but to get a new one to fail after just 100 miles of driving on a highway under perfect conditions (no rain, no wind, no dust...just perfect)... I cannot see how dirt would be responsible. The first sensor according to the mechanic was partially failed (whatever that means!)...Certainly something I can share with the mechanic! Thanks.
 

Midwestdrifter

Engineer In Residence
The new sensor must be spliced into the harness (there is no connector). I would check you mechanics splice. Also, the sensor can be reseated. I like to spritz some wd-40 around the sensor, and use a 12? 14mm? wrench to gently rotated the sensor back and forth about 20 degrees, while pushing it, it will contact the tone wheel, and adjust itself.

It is also possible that the sensor was never the problem, and you have a bad wire in the harness, or a wheel bearing thats worn and making the tone wheel wobble.
 
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hoosierrun

Active member
According to the mechanic the first sensor did not completely fail. There was intermittent contact...However, the second one was brand-new and should not be chaffed. I will share with mechanic and see what they have to say. Thank you!
Keep in mind that, if there is a wire that is rubbing or chaffed, it could anywhere on the wiring harness that goes to the module that picks up the pulses,... not necessarily on the sensor wire itself. That was what was happening in my case.
 

98Firebird

Active member
The dealer should check out LI42.45-N-053055 and see if it applies. Here is a brief description from the document.

Complaint
ESP indicator lamp lights up while driving

Fault code 441A or 445A stored in ESP control unit


Cause
Play of ABS sensor in steering knuckle


Remedy
Replace steering knuckle
 

Herve'

New member
For the sake of "partial" completeness, I wanted upon my return home provide a quick update. I will provide the next update after the problem is fixed. The ESP, ABS and skid messages have come and gone intermittently during the last week as I drove nearly an additional 1200 miles between the Florida Keys and Virginia. The ESP, ABS codes typically showed up toward the end of the day after I drove a few hundred miles and disappeared the next morning less than a mile after we started to drive again. Same happened pretty much every day except yesterday when after driving 300 miles the codes did not show at all. I will now take the van to a MB dealer with all the comments provided in this thread. At this point, unless I misread or misunderstood the above comments, it seems that the wheel speed sensors are just fine and that the problem is elsewhere around these sensors.
 
I replaced both front wheel speed ABS sensor with Mercedes Benz ABS sensors after a MB certified mechanic scanned the car for the code of the failing component...
Can you explain this part?

A code is not a diagnosis. A code is where diagnosis BEGINS. So replacing parts based solely on a code, is simply guessing.

And what is an "MB certified mechanic"? There are Mercedes-Benz factory-trained technicians, but in the year 2019, anyone who refers to themselves as a "mechanic", probably isn't one. Vehicle repair technicians have been referred to as "technicians" for decades.

And Mercedes-Benz factory-trained technicians are not trained to guess.
 

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