Replacing Wheel Speed Sensor

[Teuobk]

Hi guys. I posted this write-up in a separate thread, and several people suggested that I replicate it here. Between the time I first posted it (9/06) and now, I've used the procedure yet again to locate a failed speed sensor. For those keeping score, that means I've replaced three of the four sensors on my 540i in the past two years.

The actual sensor replacement is trivial; the tricky part is figuring out which sensor failed. I hope that this can help somebody!

----

Replacement of Wheel Speed Sensor
E39 BMW

Synopsis: A malfunctioning wheel speed sensor can cause the anti-lock braking and traction control systems to become disabled, among other things.

Symptoms: Three lights appear simultaneously on the dashboard: ABS, an amber BRAKE, and the triangular "traction lost" icon. Traction control is not operational, nor is antilock braking. One or more of the speedometer, odometer, or cruise control might also be inoperable.

Tools required: Multimeter capable of testing diodes. 5 mm Allen wrench. Long, very narrow probes for multimeter, or equivalent. For rear sensors, a 10 mm socket, 8 mm socket, flat-head screwdriver, and needle-nose pliers might be required to remove trim.

Difficulty: Easy

Diagnosis: A BMW service computer can isolate the source of the problem; standard OBDII code readers cannot pull the requisite information. The Peake Research code reader seems to be capable of reporting whether or not a problem exists, but there do not appear to be any codes that reveal the location of the faulty sensor. If a wheel speed sensor is suspected, and no computer is available, the identification process is one of trial and error. Jack up you car and support appropriately. Access to the sensor is considerably easier with the wheel removed, so pick a corner and remove the wheel.

It is worth noting that certain failure modes are associated with particular corners of the car. If the speedometer and odometer do not work, the driver's side rear sensor is probably bad. If the speedometer works but the cruise control does not, then the passenger side rear senor is probably bad.

Locate the sensor (mounted on the wheel carrier near the hub) and trace its wire back to a blue connector. The connector might be housed in a black plastic box. Open the hinged box if it is present. There might be a second connector next to the blue speed sensor connector; that's for the brake pad wear sensor. Pull the blue speed sensor connector out of the box and disconnect the two sides.

Deep inside the sensor side of the connector, there are two metal prongs. Now comes the tricky part. Turn the mutimeter on and to its diode testing setting (it looks like an arrow with a line in front of it). Connect one probe to one of the prongs, and the other probe to the other prong. The meter should read ~1.4-1.8 V or indicate an "open" condition (e.g., "OL"). Reverse the probes. Once again, the meter should indicate either an open condition or a 1.4-1.8 V drop, but the result should be whichever one you didn't see the first time. If you see any other result, such as 600 mV in each direction or 0.0 V in either direction, you've probably found the bad sensor; congratulations! Note that a 0.0 V drop is possibly indicative of a poor test setup; verify that you are not shorting the multimeter probes. If the sensor tests out okay, try again at a different wheel. Of course, it's always possible that one of your speed sensors has failed in a way that wouldn't present itself in this test. In the worst case, you'd have to go to the dealer anyway for the diagnosis.

You might want to try another wheel even if you think you found the bad sensor in order to confirm that your technique is good. It's sometimes a bit tricky to get a good connection to those prongs. If you think you found two bad sensors, you probably messed up.

Be sure to reconnect all of the sensors that you believe are good. Once you have identified the faulty sensor, obtain a replacement BMW part. One sensor on my 540i was $120; I've read reports of them retailing for as little as $70.

Other possible causes: Reports indicate that the cause of the sensor failure might be a frayed wheel-speed sensor wire in the wheel well; inspect the entire visible run of the cable carefully to confirm the lack of frayed or pinched wires. If frayed wires are found, attempt repair using common wire-repair techniques. Other reports indicate that a bad ABS controller might cause similar symptoms.

Replacement: With the wheel off at the corner with the broken sensor, and the sensor cable disconnected, unsnap the sensor wire from the two mount points on the steering knuckle. Follow the cable to the point where it ends at the sensor. The sensor is attached to the car with one or two small bolts. A 5mm Allen wrench is required to remove the bolts. You might have to do this blind, but it's not that hard. After the bolts are removed, gently pull the sensor straight out of its hole. Put the new sensor where the old one was, and reverse the removal process. There were two bolts holding my old front sensor, but the new front sensor included only one mounting hole. Due to the sensor construction, I don't believe it is a problem to use only one bolt. Be sure to hook the new sensor back to the other connector, and don't forget to snap the cable into the cable brackets.

Commentary: I have had three speed sensors fail on my 1999 540i. The first time, a front sensor failed. The DSC, ABS, and brake warning lights were be off when the car was first started but would turn on after driving a couple hundred feet. A year later, a rear sensor failed. The same three lights shone at startup and never reset. The Peake reader indicated code 0F 78. A few months after that, I had another rear sensor fail. I was able to use the above procedure all three times to successfully locate the failed sensor.

---

Jeff
____________________________
Edit: Here is a DIY with pics from M5board.com.
http://www.m5board.com/vbulletin/e39...front-diy.html

jamesdc4

[herc97]

i have that triangler light come on when i first start my car up . then i drive to work, park and then come down stairs and start it back up and the light goes off i think this is helpful i will check these sensors!

[koko164]

Does anyone know where I can obtain the male end of the blue connector on the Wheel Speed Sensor cable? Mine have all started to crumble away and i note they are easy to remove but can't find anywhere that I can obtain new ones.

[wintersm]

Jeff,

Thanks for the post. It sounds like you've replaced enough of these to know what you're doing. Maybe you know what I'm doing wrong? When I test the sensor with diode test on my multi-meter, I get either a steady "1" or if I reverse the direction I get a jump to just under 2000, then back down to 1 (very fast). If I test the resistance in either direction I get the same value of 160,000 Ohms (give or take). This happens for all 4 sensors and I still get the standard BRAKE, ABS, and DSC indicators illuminated after a few miles of driving.

Any suggestions?

[gtxragtop]

The sensors I suspect are hall effect sensors. They generate a voltage pulse when the wheel is spun. Hence you want to measure millivolts not ohms. The faster you spin the wheel, the more voltage it will generate. Ideally, you look at the pulses with an oscilloscope since this will give a very accurate look at what the sensor is doing.

Jeff,

Thanks for the post. It sounds like you've replaced enough of these to know what you're doing. Maybe you know what I'm doing wrong? When I test the sensor with diode test on my multi-meter, I get either a steady "1" or if I reverse the direction I get a jump to just under 2000, then back down to 1 (very fast). If I test the resistance in either direction I get the same value of 160,000 Ohms (give or take). This happens for all 4 sensors and I still get the standard BRAKE, ABS, and DSC indicators illuminated after a few miles of driving.

Any suggestions?

[knux11]

old thread, but should help me in the near future. thanks!!

[VasceBimmer]

I need some assistance here. The dealer showed me the code printouts. It says front left speed sensor. Now... The tech told me to change the speed sensor and the ASC module because the faulty sensors generally cause the modules to fail also. I'm not sure if I'm buying that advice. I want to change the speed sensor. Will I need to reset the fault or will it correct itself after the replacement? I would like to know because I do not have a computer.

[knux11]

it will resolve itself. just change the sensor, it's real easy and it's an 80 dollar part. More thru stealer. but replacing the asc module is a waste of money at this point.

[VasceBimmer]

Awesome! Thanks. Let's see how it goes.

[blackraven15205]

Thank you again as many have for this. You saved me lots of time and tons of money. My speedometer was out in my '01 530i and needed it to pass inspection, $23! on Ebay for a brand new direct fit OEM aftermarket sensor. Followed the details, and worked perfect!

[mikejbmw]

Early '97 540i

Anyone else try the cheap ABS sensors? I assume this is a Chinese part, do they work, any longevity here?

[tru350z]

Thank you very much for useful information.

I have tried to take the rear sensor out but plastic peice broke.
Is it ok to drill out the hole? Is it open end from the hub?

[gjp111]

Please provide any information that may help.
My speedometer and vacum gagues as well as my odometer are intermittent. If the car sits for a day or so thay will work fine for about 5 or 10 minutes then out for the rest of the day. The ABS & DSC lights never light not even when I first turn on the key any check all other lights. I believe the wheel sensors are ok but not sure because of the intermittent problem. Does anyone have any suggestions for me? Is it possible the sensor box in the console is bad? Or the abs unit? I would think either would produce a constant ABS DSC light but I have no lights ever.

[jregier]

Hey Guys... My DSC light comes on only when i turn right at speed. When i'm going slow and making right hand turns in town, nothing happens but when i am on the hiway and take an off ramp or slightly more aggressive right hand curve the light comes on, the engine cuts power and the cruise cuts out. After i straighten up the light goes off and i'm able to accelerate again. this must be a speed sensor but any clues to narrow it down?

thanks

[Teleplayer]

Hey Guys... My DSC light comes on only when i turn right at speed. When i'm going slow and making right hand turns in town, nothing happens but when i am on the hiway and take an off ramp or slightly more aggressive right hand curve the light comes on, the engine cuts power and the cruise cuts out. After i straighten up the light goes off and i'm able to accelerate again. this must be a speed sensor but any clues to narrow it down?

thanks

If cruise control turns off, I think you may want to check the passenger side rear sensor:

If the speedometer and odometer do not work, the driver's side rear sensor is probably bad. If the speedometer works but the cruise control does not, then the passenger side rear senor is probably bad.

Mine's a 98 528i, and all but one sensor was bad. It was obvious, too.. once I looked under the car. If you jack it up and remove the tire, you should be able to follow it from the sensor to the connector... it's possible that you will see that it is frayed, but you may need to use a multimeter to make sure.

Steve

[anacondatcu]

Hey Guys... My DSC light comes on only when i turn right at speed. When i'm going slow and making right hand turns in town, nothing happens but when i am on the hiway and take an off ramp or slightly more aggressive right hand curve the light comes on, the engine cuts power and the cruise cuts out. After i straighten up the light goes off and i'm able to accelerate again. this must be a speed sensor but any clues to narrow it down?

thanks

i'm experiencing a similar cut in power but it happens sometimes trying to accelerate normally, turning on the DSC light until i release the gas for a few seconds, it also turns off the cruise until i restart the car. Please let me know if you do anything to further diagnose the wheel speed sensors

[postkent]

my windshield wiper dont work when i pull the handle in ,one speed work but i have to hold it

oh its a 1999 528i

[kopka]

Hi guys. I posted this write-up in a separate thread, and several people suggested that I replicate it here. Between the time I first posted it (9/06) and now, I've used the procedure yet again to locate a failed speed sensor. For those keeping score, that means I've replaced three of the four sensors on my 540i in the past two years.

The actual sensor replacement is trivial; the tricky part is figuring out which sensor failed. I hope that this can help somebody!

----

Replacement of Wheel Speed Sensor
E39 BMW

Synopsis: A malfunctioning wheel speed sensor can cause the anti-lock braking and traction control systems to become disabled, among other things.

Symptoms: Three lights appear simultaneously on the dashboard: ABS, an amber BRAKE, and the triangular "traction lost" icon. Traction control is not operational, nor is antilock braking. One or more of the speedometer, odometer, or cruise control might also be inoperable.

Tools required: Multimeter capable of testing diodes. 5 mm Allen wrench. Long, very narrow probes for multimeter, or equivalent. For rear sensors, a 10 mm socket, 8 mm socket, flat-head screwdriver, and needle-nose pliers might be required to remove trim.

Difficulty: Easy

Diagnosis: A BMW service computer can isolate the source of the problem; standard OBDII code readers cannot pull the requisite information. The Peake Research code reader seems to be capable of reporting whether or not a problem exists, but there do not appear to be any codes that reveal the location of the faulty sensor. If a wheel speed sensor is suspected, and no computer is available, the identification process is one of trial and error. Jack up you car and support appropriately. Access to the sensor is considerably easier with the wheel removed, so pick a corner and remove the wheel.

It is worth noting that certain failure modes are associated with particular corners of the car. If the speedometer and odometer do not work, the driver's side rear sensor is probably bad. If the speedometer works but the cruise control does not, then the passenger side rear senor is probably bad.

Locate the sensor (mounted on the wheel carrier near the hub) and trace its wire back to a blue connector. The connector might be housed in a black plastic box. Open the hinged box if it is present. There might be a second connector next to the blue speed sensor connector; that's for the brake pad wear sensor. Pull the blue speed sensor connector out of the box and disconnect the two sides.

Deep inside the sensor side of the connector, there are two metal prongs. Now comes the tricky part. Turn the mutimeter on and to its diode testing setting (it looks like an arrow with a line in front of it). Connect one probe to one of the prongs, and the other probe to the other prong. The meter should read ~1.4-1.8 V or indicate an "open" condition (e.g., "OL"). Reverse the probes. Once again, the meter should indicate either an open condition or a 1.4-1.8 V drop, but the result should be whichever one you didn't see the first time. If you see any other result, such as 600 mV in each direction or 0.0 V in either direction, you've probably found the bad sensor; congratulations! Note that a 0.0 V drop is possibly indicative of a poor test setup; verify that you are not shorting the multimeter probes. If the sensor tests out okay, try again at a different wheel. Of course, it's always possible that one of your speed sensors has failed in a way that wouldn't present itself in this test. In the worst case, you'd have to go to the dealer anyway for the diagnosis.

You might want to try another wheel even if you think you found the bad sensor in order to confirm that your technique is good. It's sometimes a bit tricky to get a good connection to those prongs. If you think you found two bad sensors, you probably messed up.

Be sure to reconnect all of the sensors that you believe are good. Once you have identified the faulty sensor, obtain a replacement BMW part. One sensor on my 540i was $120; I've read reports of them retailing for as little as $70.

Other possible causes: Reports indicate that the cause of the sensor failure might be a frayed wheel-speed sensor wire in the wheel well; inspect the entire visible run of the cable carefully to confirm the lack of frayed or pinched wires. If frayed wires are found, attempt repair using common wire-repair techniques. Other reports indicate that a bad ABS controller might cause similar symptoms.

Replacement: With the wheel off at the corner with the broken sensor, and the sensor cable disconnected, unsnap the sensor wire from the two mount points on the steering knuckle. Follow the cable to the point where it ends at the sensor. The sensor is attached to the car with one or two small bolts. A 5mm Allen wrench is required to remove the bolts. You might have to do this blind, but it's not that hard. After the bolts are removed, gently pull the sensor straight out of its hole. Put the new sensor where the old one was, and reverse the removal process. There were two bolts holding my old front sensor, but the new front sensor included only one mounting hole. Due to the sensor construction, I don't believe it is a problem to use only one bolt. Be sure to hook the new sensor back to the other connector, and don't forget to snap the cable into the cable brackets.

Commentary: I have had three speed sensors fail on my 1999 540i. The first time, a front sensor failed. The DSC, ABS, and brake warning lights were be off when the car was first started but would turn on after driving a couple hundred feet. A year later, a rear sensor failed. The same three lights shone at startup and never reset. The Peake reader indicated code 0F 78. A few months after that, I had another rear sensor fail. I was able to use the above procedure all three times to successfully locate the failed sensor.

---

Jeff
____________________________
Edit: Here is a DIY with pics from M5board.com.
http://www.m5board.com/vbulletin/e39...front-diy.html

jamesdc4

Jeff,
This helped me on my 1987 325. Left front wheel speed sensor wires were broke (inside insulation) at the strain relief (bracket on shock). Stirpped wires, soldered & covered with heat strink tubing. Good as new. Thanks for the tips.

Jeff

[dinot71]

Can someone please tell me how many Speed sensors a E39 5-Series has? Is there one in each corner or just where the pas wearing sensors are located?

email: dinot71@gmail.com

[dinot71]

How many ABS speed sensors does the E39 have? 4? 2?

[repandpresent]

4

[dinot71]

Are there any tricks on removing the rear ABS sensor, I can see its easy to remove it from the caliper but how about the other end? It looks like is wedged up in there.

[bagodonuts68]

thanks to jeff for the original post outlining the steps to diagnose wheel speed sensor issues in the e39. Following his directions my multimeter in the diode setting reads 1 regardless of polarity and regardless of where i check (at multiconnector under the hood or at the sensor in the wheel well....hmph).

does the control module need to be present to check wheel speed sensors? My module is out to get fixed at BBA. i want to make sure the sensors are good before i plug the rebuilt module back in. I am thinking it needs to be plugged in to get a reading. if so, am i at risk of damaging the module again by installing it into the car with a bad wheel speed sensor??

[Longshot512]

Thanks for the write up! I have that exact issue and was trying to figure out where to start troubleshooting. For anyone else out there that has those lights poppin' up and wants to replace the sensor: check out the link I added, pretty cheap prices on there.

http://www.usedpartslive.com/catalog...mk=BMW&md=525i

[MKpoto]

great write up, I have this same issue but never really minded it