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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 08-11-2009, 10:23 AM   #1
beberle
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DIY: Removing / Cleaning ABS Speed Sensors

I've been dealing w/ the dreaded 'triple play' of ABS/DSC/Brake lights. Took it to the dealer and they wanted to replace the control module for $1,500. I asked if that's what the codes read.. they said there weren't any codes, so replacing the module was 'troubleshooting'
Since I've got no codes, I decided to clean the front speed sensors. It's fairly easy, but I haven't seen a DIY here... and now there is.

My 323it has 170k miles on it. The speed sensors are heald on by a simple hex-head bolt. Be careful, one of the mounting bolts snapped when I tried removing it. They're supposed to be torqued to 8nm. Probably took 25nm to remove the one that survived. They are corroded and frozen from years of heat. Also, it seems that the bolts are luminum vs the iron wheel hubs?

In order not to break the speed sensors, I used a large flat-head screwdriver to pry the sensor straight out. Just get the head under the mounting flange and 'twist'. Even after 170k miles, they moved fairly easily up. Continue to carefully 'work' the sensor straight out. I also used an adjustable wrench to twist the sensor w/ the screwdriver prying up.

Both sensors had a large amount of metal shavings on them. I used a moist paper towel to remove the shavings. Use anti-seize compound on the sensor barrel before reinstalling. I used a socket and rubber mallet to tap the sensor back into place. re-torque bolt to 8nm.

I unplugged the batter for 15min to clear lights. However, the lights were still on when I plugged the battery back. The lights went out after 10 minutes of driving. We'll see how long it lasts....

Note: the problem started shortly after I put in new front brake rotors. I originally thought I had damaged a sensor or wire. I now believe that new rotors/pads just produced enough metal shavings to push the sensors over-the-edge of sensitivity.
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Last edited by beberle; 08-14-2009 at 12:18 PM.
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Old 08-11-2009, 07:50 PM   #2
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Good info. I guess that's the new BMW way...just start replacing parts.
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Old 08-11-2009, 09:20 PM   #3
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I struggled with my rear sensors trying to get them out (after 120K) tried screwdrivers, PBblaster, small vice-grips, etc. and eventually gave up and had my local Indy handle it as part of some other stuff he was doing for me. They wound up having to break one off and fish a bunch of broken pieces out of the hub as it was basically fused into the hub. Hope your cleaning works as these things are electro-magnetic and over time just start to wear out.
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Old 08-14-2009, 12:32 PM   #4
beberle
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Rear Sensors

Turns out that the ABS kicked-in and the lights came back on for my wife before getting out of the subdivision.. So, I just removed and cleaned the rear sensors this morning. On my 2000 323it w/ 170k miles, the rear sensors were VERY easy to remove. The sensor has 'tabs' or ridges on the body, so not the entire sensor is touching the mounting hole. I just removed the hex bolts and gave the sensor a light twist. Came straight out.
I read somewhere about checking the sensor by using a voltmeter and turning the wheel/hub to detect 1 to 5mv. I wish I had done that Before cleaning the sensors. The left/rear sensor wasn't very dirty. The right/rear sensor was covered in crud.
I cleaned the sensors and had to mount the rim back on the hub to turn the rear hubs (2 lug bolts finger tight). Also had to drill a 1/16th hole in the side of the sensor shroud to get one probe on a contact while the other probe came through the top. both sensors showed between 2 and 8mv. The voltage bounced all over the place, but I get the feeling that any output is a good thing.
Put everything back together and the ABS/DSC/Brake lights went out within 20ft of the garage. I drove it 15miles each-way on an errand in stop-n-go traffic. No lights, no ABS.
Note: The rear sensors have 3 metal 'plates' exposed on the end of the sensor vs. the plastic-covered front sensors. If these things generate small electric pulses... an epiphany just struck.... Pulse Generators!!! then metallic crud shorting the metal plates on the the rear sensors would short out any voltage generation. Wish I had checked w/ the multi-meter to confirm this Before cleaning the sensors. Because of the exposed metal plates, I would recommend cleaning the rear sensors 1st troubleshooting any DSC problem.
I spent MANY hours under the car troubleshooting this one
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Old 08-15-2009, 06:53 AM   #5
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Good work, glad you were able to solve the problem simply.
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Old 08-23-2009, 10:32 AM   #6
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Let us know if u still get the ABS/DSC/BRAKE lights on after some driving
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Old 08-24-2009, 05:00 AM   #7
beberle
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We've put 700 miles on it already without a single problem. Just got back from serious driving in the North Georgia mountains, including some dirt roads. Gotta' love the Sport Wagon!
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Old 09-08-2009, 11:14 AM   #8
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AWesome! thank you a ton for this write up. Will give it a try as I have the same simptoms except. I get the EML light coming on as well. Thanks
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Old 09-12-2009, 12:24 AM   #9
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Originally Posted by grafiksguy View Post
I struggled with my rear sensors trying to get them out (after 120K) tried screwdrivers, PBblaster, small vice-grips, etc. and eventually gave up and had my local Indy handle it as part of some other stuff he was doing for me. They wound up having to break one off and fish a bunch of broken pieces out of the hub as it was basically fused into the hub. Hope your cleaning works as these things are electro-magnetic and over time just start to wear out.
My driver-side sensor snapped in half leaving the part that is inside the hub flush with the hole on the outside. This happened a week ago and I haven't worked up the courage to deal with it. Maybe I'll just wait until I decide to do the wheel bearing and then I can just hammer the thing into the hub and take it out from the inside.

Interestingly my passenger-side sensor came right out.
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Old 10-23-2009, 06:36 AM   #10
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Hi I have the same problem with these abs/dsc/brake lights,come and off
every now and then , but now the speedo on the dash as how stop working ,and the petrol light keeps come on, but the there it plenty petrol in the tank. did these faults happen then your abs/speed sensor failed.

James.
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Old 10-23-2009, 07:06 AM   #11
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Sierragli... do a search on speed sensors; one of the rear sensors affects the sensors, I forget which one.

UPDATE: after about 2k miles, the lights started to come back on intermittently. Because they went away when I cleaned the rear sensors, I replaced both rear. Lights immediately went out and have stayed out. I paid $75 each for OEM sensors at Pelican parts. They might be cheaper elsewhere. Make sure you go with OEM supplier; I've read that non-oem might be cheaper, but might not work well with the computer.
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Old 10-23-2009, 07:08 AM   #12
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Hey Frog,
I don't think that part of the hub is sealed. Look from underneath... there appears to be a gap that you can see the ABS ring from. Not sure how big the piece is, but it might fit through the gap...

Luck!
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Old 10-24-2009, 11:11 AM   #13
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Hi , UPDATE :- Went and bought a new rear abs/speed sensor, on starting my car just after leaving the EURO parts shop the abs /dsc/brake lights came on, after I released the hand brake the brake light went out, after driving about 200 yds the abs/dsc lights went out , about anther 100 yds the petrol light went out ,after stopping at traffic lights the speedo started working again, the lights have stayed out and the speedo has worked fine all day after a few trips here and there.
I wonder what would have happened if I had actually fitted the sensor in stead of just putting on the passenger seat ha ha
Know doubt the lights will return
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Old 10-24-2009, 12:52 PM   #14
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Wow. BMW Dealership Service Department are pointless!

If you go in with a problem they always tend to troubleshoot MOST EXPENSIVE thing to replace first to MOST OBVIOUS cause of the issue last.
$1500 to replace a module when all they had to do was clean and test the sensors individually with a voltmeter and replace each $75 sensor pair as needed.

I'd really like to attend one of the dealership's morning management meetings to see what their mission statement really is and how that reflects down to basic and honest customer service.

That is just horrible in this economy that business practices are so greedy!

I don't even think Drug Dealers and Drug Cartels are so cut throat when it comes to customer service.
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Old 11-13-2009, 06:30 AM   #15
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Hi, Update :- my trio of lights(abs/ dsc /brake light) came back on again yesterday
and with the speedo needle at zero and the fuel light coming on and off, so I decided on changing the rear left wheel abs/speed sensor
not as easy to get out as some of the other posts say, but then eventually got the new one in , and started the car up and took it for a spin and all the f----n lights there out and the speedo and fuel light are back to normal.

Last edited by sierragli; 11-13-2009 at 07:24 AM.
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Old 11-16-2009, 04:36 PM   #16
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Thought I'd chime in on this since it happened to me also. My dsc/abs/ brake light would all light up and gas gauge would fluctuate dramatically when it got below half tank with my speedo cutting in and out. Come to find out I was driving without dsc and abs this whole time when I brought it to an indy shop to run codes. They told me it was my abs module and it would cost $1100 and 3 hours of labor. Now I originally searched this problem on here and had some clue what the problem was and just wanted them to run the codes. When I asked to see the codes it came up as my wheel speed sensor and they went into a long bs explanation on how the abs module was shot and that effected the sensor. So I told them I didn't think it was the abs mod and to just replace the sensor and they quoted me $200 for the part and 2 hours labor!!! I ended up buying the part on Tischer for $135 and spent a whole 15 min replacing the thing, hardest part was probably taking off the tire lol. No problems so far after 50 miles.
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Old 02-15-2010, 01:18 AM   #17
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That's fu*king awesome!!!
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Old 02-16-2010, 12:23 PM   #18
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I've always removed the sensors on my car by soaking the bolts with penetrating oil the night before. When a sensor refuses to play nice - come out without too much of a fight - I remove that sensor's wheeel, caliper and brake bracket. I then use the plastic butt of an old screwdriver and tap the sensor out from the business side. When that fails (only once!), it's time for a new sensor.
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Old 02-17-2010, 02:12 PM   #19
dallas320i
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Quote:
Originally Posted by sierragli View Post
Hi I have the same problem with these abs/dsc/brake lights,come and off
every now and then , but now the speedo on the dash as how stop working ,and the petrol light keeps come on, but the there it plenty petrol in the tank. did these faults happen then your abs/speed sensor failed.

James.
Mate, I had same problem, these ABS sensors works like Hall effects sensors,
so you can't test this using usual multimeter. And they are also slow-dying,
you may clean this, but this is for short time period.
I've replaced one rear after 256000 kilometers, seems I had original from 1999.

Rear left sensor works for speedo- and economizer gauge, I also had same
story with fuel gauge. I guess when car is "not driving" (speedometer =0) ,
in this case jet pump not works (second fuel pump inside tank which pump
fuel from one half of tank to another). So if you check your tank level via PC
(for example INPA software) or via meter panel test mode, you will see low
level in one half, and almost full second half of the tank.

From the other side, maybe I am not 100% correct, as some sources says
that jet pump is completely passive hydravlic system and has no electrical
parts even valve, but I can't find any other reason to my mind.

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Old 02-17-2010, 04:47 PM   #20
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my problem is the same but different my abs light is always on and the car still breaks fine but when the abs light turns off i here the brakes grinding as i slow down then when i come to a complete stop the abs light turns on and it works good again
anyone know what i might have to do
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