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Old 11-02-2002, 12:13 PM
Registered User
Join Date: Aug 2002
Location: Princeton, NJ
Posts: 44
ABS Speed Sensor !!!! 126 560 SEL

Is there a trick associated with removing the ABS speed sensor?

I got the screw off just fine but cannot get the sensor out!

I have pulled and leveraged and done everything I can but can't get the darn thing out.

Am trying to do this on the driver side FRONT wheel.

Any thoughts, advice ?
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Old 11-03-2002, 09:52 AM
Registered User
Join Date: Jul 2000
Posts: 638
stuck ABS sensor

Try squirting some penetrating oil around it after you have cleaned the area real well with brake cleaner. Then careful application of heat from a pencil size propane torch around the sensor, not on it, and then chill the sensor with ice or a spray of brake cleaner or refrigerant. The temperature difference may help break the bond.
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Old 11-08-2002, 11:22 PM
Registered User
Join Date: Aug 2002
Location: Princeton, NJ
Posts: 44
Angry ABS - am losing it!!!! H E L P!!

I finally got the sensor out. Phew! It had some grunge on it, I installed the new one ..... started the car up and the second I put it in drive - the ABS light comes on!!!

Right before, the light would come on in a little bit and if I braked during that period, with the light not on, the pedal would pulse.

That has stopped - not sure if that is a good thing, or, bad thing.

Then, I removed both fuses from the OVP, whicle the car was running, both were fine, so I plugged them back in. Shut the car and boom - light came on!

Did the same with the car off - no change.

What in the world am I doing wrong?? The OVP is new, I changed it about a month or so ago - I first thought that would kill the ABS light - it didn't. Not sure if the OVP blew again .... dunno how and why that would happen.

Please PLEASE help?? I spent three hours with this, this evening!!
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Old 11-09-2002, 03:01 AM
MikeTangas's Avatar
Senior Member
Join Date: Apr 2000
Location: So. Cal
Posts: 4,430
Did you check & clean, or replace the passenger side sensor too?
Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon least its a diesel

Non illegitemae carborundum.
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Old 11-09-2002, 01:53 PM
Registered User
Join Date: Aug 2002
Location: Princeton, NJ
Posts: 44
Hi Mike

I changed just the driver side, front sensor. These are very hard to get out! I thought about trying it ... but was tired. The old one didn't look awfully dirty.... the reason I did that side is because I got suckered into having it "looked at" for 50 bucks that turned into a 125 bucks and all he told me is that the driver speed sensor is out. Yes, serves me right, I thought this mechanic would know better and had the equipment .... nah! It's tough finding a trustworthy person.

With winter rapidily approaching - I need the ABS to work - - I will try to give it another go - or I will take it into the Benz dealership and get fleeced willingly!

Sorry, I am complaining, I am tired and frustrated!
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Old 11-10-2002, 12:13 PM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
The speed sensor is monitored in at least a couple different ways. It is monitored for internal resistance/resistance to ground and its output as a signal generator. In the second activity the various readings for other sensors are used to compare readings of "mapped" values. If the car is going straight (as determined by three confirming wheel speed signals), then a fourth disagreeing value will be faulted (in ASR 4 sensor systems). If it is in a right turn the left front sensor will be traveling the fastest and the right rear the slowest.

In a article I wrote about BMW transmissions there is a scope pattern of the digetized speed signals coming to the trans controller. There are two 4 channel patterns at the end of the article, one in straight driving and the other in a hard turn:

The first type of failure is seen on startup during the selftest. The second type of failure is performance based and occurs once 10kph is reached and is continuous. In your situation the type of failure has changed and there isn't any direct reason. You now have something that isn't passing the selftest. The sensor can only fail the selftest due to resistance problems. Since you now have different type of failure it could be for most anything. The OVP only powers the ABS controller, not the light. It takes a manifest decision by the controller to turn out the light. The light will be on if the controller is removed from the car.

One point I might make about purchasing diagnostics: Almost all diagnostic fault trees leave the technician at this point: try known good device and retest. If one is buying diagnostics by the drop so that one can then purchase said component more cheaply, then one has become part of the diagnostic process.

I do regular testing for numerous other shops. They all wish to make the money on parts from my diagnostic. I let them buy as much of my testing and intelligent speculation as they wish, BUT if they wish a finished product with a warrantee I provide the parts.

LET ME TELL YOU WHY. Diagnostics done well is a bunch of speculation. It needs to be that way, this is not scientific research and recieves no government spending. Using, seat of the pants statistics, thorough knowledge, and all the testing technique (known to mankind) a good diagnostician can determine that the ABS controller is probably the problem (say for instance). There is no way to prove it except substitution. If that tech is so equipted with a ready substitute then diagnostics is easily finished. If NOT then either the shop has to warrant the diagnosis or the customer has to (by accepting parts that don't fix problems). The state of diagnostic risk described here is maximum for control units which can't be tested in the field, but all diagnostics is a work in progress till the final repair is finished. The level of testing is thus left to the one extending warrantee. If left in the hands of an honest professional one will buy only the parts needed and leave with a warrantee.
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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