E39 Wheel Speed Sensor Replacement

[Teuobk]

Hi guys. I just got done replacing one of my ABS/DSC wheel speed sensors on my 540i and thought I'd write about it. I've had two sensors fail over the past two years, and I was able to use the concepts below both times. The actual sensor replacement is trivial; the tricky part is figuring out which sensor failed. I hope that this can help somebody!

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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 two 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. I was able to use the above procedure both times to successfully locate the failed sensor.

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Jeff

[Hotswimmer]

Hey Jeff,

Thank you very much for taking the time to post this. Could I suggest that you also post it to the E39 FAQ thread in this forum so it's easier for people to locate and it doesn't just disappear in a few days?

Thanks again.

[ataie]

so were is the sensor itself? left or right rear? thanks

[masurati]

so if rear wheel sensor is unpluged odometer stops counting miles?

[ataie]

ok, I had the ABS, DSC, brake, and check engine lights on. All amber.

check engine code was 500, which is wheel speed sensor. My mechanic replaced the sensor and cleared the engine code. The ABS, DSC and brake light still remained on. after driving for about 25 miles the check engine light came back on. code 500 - wheel speed sensor. so what next? do I need to change the front one now? what else can I check? thanks

[ataie]

can git rid of the light....

I've changed both rear and one front sensor (one at the time to save money), and after 20 miles or so the 'check engine' light comes on with code P0500 which is speed sensor.

the ABS, DSC, & 'brake' lights remain on in amber. some mornings when the car is started there is no light on, then about 2-3 miles they come back on.

what next???

[ataie]

now ALL 4 wheel sensors have been changed- 3 lights remain on along with 'CEL' reading code P0500. would a faulty ABS module case all these lights to come on?

[KOLYAtheDJ]

what if my DSC light is on, and both speedometer and cruise control are working?
DSC light comes on every time i pass 17.5 mph when i start the car and stays on until i turn the car off.
any thoughts

[fuddyduddy121]

now ALL 4 wheel sensors have been changed- 3 lights remain on along with 'CEL' reading code P0500. would a faulty ABS module case all these lights to come on?

I'm wondering where the main speed sensor really is - is it on the driveshaft or one of the wheels?

[ataie]

anyone know how to reset the DSC??? dealer what's to charge one hour labor to do it.

new ABS module as well as 4 new wheel speed sensors. ABS, DSC, brake lights are on. Peake reader gives me error on this car, and OBDII doesn't see any code. I just need to reset it.

[Dan]

Hey Jeff,

Thank you very much for taking the time to post this. Could I suggest that you also post it to the E39 FAQ thread in this forum so it's easier for people to locate and it doesn't just disappear in a few days?

Thanks again.

i sent him an email about this... good call Randy! good write-up's like this is what the FAQ needs.

[biyiojones]

Thanks a lot for the procedure it realy help, it worked with mine. it saved me a lot of money , i was able to fix the abs sensor by just doing some wire repair.

[Weboddity]

My 528i has all of the symptoms described. The speedometer, odometer and cruise control were working every morning for my ~7 mile trip to work, where I turn the car off for about ten minutes. When I start the vehicle again none of those things work and pretty much won't work for the rest of the day, though occasionally they kick back on. I start my car again at least 3 more times from that point to the end of the day. I had the sensors swapped from left to right in the rear and now it doesn't work at all.

I am going to replace the rear sensors and post an update. Thank you for this post.

[bimmerfiver]

Good post man.

Here is my BMW Peake Scanner Model R2D2. He works my codes:

[mefff]

Good post...just a little additional info.... No matter how careful you are and after the sensor breaks at the hub housing like both mine did... don't sweat the small stuff. Just give it a real good spray around the outside with wd40 or Liquid Wrench or whatever you prefer. Then gently tap behind the broken part all the way round with a small punch to loosen it. After about 10 minutes firmly pull on the remaining broken part. If it rips off at the wires like mine both did.... simply use a 1/8 drill and drill into the remaining piece about 1 inch... now screw a metal screw a little larger than 1/8th firmly into the drilled hole. Next put a pair of long nose pliers below the neck of the screw sticking out and pry from behind on the pliers with a small bar or screwdriver. It'll come strait out with a bit of work. After its removed, take your garden hose and firmly spray into the sensor hole to remove any mud or gravel from the sensor. Mine were both full of crap. A little wd40 on the new one and she slides right in.
Regards Mefff

[Weboddity]

I am going to replace the rear sensors and post an update. Thank you for this post.

I replaced the rear sensors, which has not corrected my problem (see my previous post). The speedometer has gone back to intermittently (but usually not at all) working.

I spoke to someone I know that works on BMWs for a dealership, who said that the problem is most commonly a result of a bad DSC module. He said that the modules going bad is a common problem, and that it is the most likely and hence should be my starting point. He then said that if that failed, it could be because of what BMW calls the Komvi, which from what it sounds like a lot of things report to and is also responsible for the display of the mileage.

He said that the dealership has often replaced the Komvi unit if the display of mileage has a bad pixel as a "good will" fix, and seemed to indicate that they kind of did it because the mileage has to be properly displayed (legally?); he is unsure of whether or not the dealership would replace the Komvi if it is bad but has a proper display of pixels.

I think my smartest next step would be to pay a business to diagnose the problem via a computer. That way I don't drop even more money without being absolutely certain that the problem will go away.

[FP5241]

bump...

[JShare]

I was working on my 740iL so it should be the same for the E39 I imagine. First, thanks for the original post. Checking these things is a bit of a pain so some details may save you some time. I have checked all my wheel sensors and this is what I came up with.

Front: If you are not inclined to pull the wheels you do not need to. If you are checking the left front then turn the wheel to the right and get at the conection box from the rear side of the wheel and vs versa for the right. The box hinges forward. A flathead help with getting it open. Once I had it open I tried using two aligator clips. This is too big. I successfully used one aligator and one wire. Eventually I went to using two wires. The way I did it was cut about a 3 inch piece of wire and strip one side. I then took the probe of my multmeter and de-virginized the non-stripped end so it slide over the pin a little easier. I then took each wire and slide the non-stripped end over each pin in the wheel sensor connector, so you end up two wires with the stripped end hanging out, ready to be tested. The values I got on my fluke were about a 1.97-1.99 v Drop for all four. I after I checked each with the multimeter I cranked the wheel back the other way and pulled the sensor and visually checked it. I ended up bending one of the pins slightly and just bend it back with my pinky.

Rear: On the first one I jacked it and pulled the wheel. On the second one I didn't pull the wheel. Of course you can't crank the wheel so it's a bit more painfull, but it was still quicker than jacking and removing the wheel. Depending on how much space you have in your wheel well and how big your forearms are it may not be an option.

Varsity move: If you don't feel you need to check the sensor visually or even if you do, why not check them from the ABS module. This would not only identify an open wheel speed sensor it would identify bad wiring between the ABS module and the sensor. The catch is you need to know which pins go to the wheel speed sensors. I have a Bosch 5.7 on the 740. I pulled the electrical conector off the control module and started checking between the pin holes with two wire and the multimeter. I found that I got a 1.97-1.99v drop and they passed the test as a diode between pins 12-28, 13-29, 30-31, 15-16. I did not spend the time figuring out which sensor goes to which pin.

Unfortunately or fortunately all my sensors checked good. This means my ASC light is probably the module itself. I am still working it.

[scushkadee]

hi. just wondering if you figured out if it was the module??

[luyckxj]

On a E39 the Electronic Control Module Connectors are:
pin 12 / pin 28 : Left Front Speed Sensor
pin 13 / pin 29 : Left Rear Speed Sensor
pin 15 / pin 16 : Right Front Speed Sensor
pin 30 / pin 31 : Right Rear Speed Sensor

See also
pag. ELE-15 of ABS/DSC controle module (A65)
or
pag. ELE-21 of ABS/ASC controle module (A52)

both in the Volume II of the
"BMW 5 Series - Service Manual" of the "Bentley Publishers"
(by the way, recommendable)
See: http://www.bentleypublishers.com/product.htm?code=B502

[Mark540i]

It is advised that during installation to apply a thin coat of Staburags NBU 12/K to speed sensor and housing.

What else can we use to grease this sucker?

[dnifong]

OK, I had all three lights. "Brake ABS and DSC." I took the car to the dealer. they told me it was the module. I sent mine to bba reman. they stated mine was not repairable, so purchased a remanufactured unit from them. 650 bucks. the new module cleared the "brake and abs lights", but not the DSC light. so I carried it back to the dealer. they said it is the steering angle sensor. WTH? can I trouble shoot this sensor before I purchase it?

thanks for your help. I have spent to much money and time to let them fix it now. dale

[jnyost]

Damn dude. I sell them for $450.

[robotz991]

I need a DSC controller for a 2001 525 built in 9/00 already replaced the fault reported, front right sensor.. nothing changed except my bank account balance..

The shop and I are confident it's the controller and not the sensor.. i need to make sure he doesnt thow that one away!!

lets talk

[jnyost]

PM replied.