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ABS Wheel Speed Sensor Replacement
 
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Pelican Technical Article:

ABS Wheel Speed Sensor Replacement

Nick Czerula

Time:

2 hours2 hrs

Tab:

$100

Talent:

****

Tools:

Phillips & flathead screwdriver, 5mm Allen bit (long)

Applicable Models:

BMW Z3 (1996-02)

Parts Required:

ABS wheel speed sensor, Molykote Longterm 2 grease

Hot Tip:

Check for fault codes before replacing

Performance Gain:

Working ABS system

Complementary Modification:

Brake fluid flush

The ABS wheel speed sensor in each wheel hub monitors road wheel rotation and sends an electronic signal to the ABS / ASC or ABS / DSC module. This signal is used to calculate road wheel speed to help with ABS braking and stability control features. 

When an ABS wheel speed sensor fails, the ABS module loses road wheel speed for the corresponding wheel and sets a fault code for the ABS wheel speed signal. When a fault code is set, the ABS warning light illuminates. Although you don't need a scan tool to replace a speed sensor per se, you have to scan the module and read the fault codes to determine which speed sensor is the problem. Keep in mind that other problems can illuminate the ABS warning light, so be sure to scan and read fault codes before replacing parts. If needed, you can swap ABS sensors side to side to see if the problem follows the sensor. If so, you know the sensor is faulty.

Wheel speed sensors are bolted to each wheel hub and are therefore susceptible to damage from impacts, road grime and brake dust. In this tech article, I will go over how to replace the front and rear wheel speed sensors.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches. Also, make sure the replacement wheel speed sensor is correct for your exact model. 

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability. 

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Lift the axle of the vehicle you are replacing ABS sensor on. See our tech article on jacking up your vehicle.

Remove the wheel from your vehicle.

Front ABS sensor:

Working behind front strut (yellow arrow), open plastic door (green arrow) for ABS sensor electrical connector.
Figure 1

Working behind front strut (yellow arrow), open plastic door (green arrow) for ABS sensor electrical connector.

Pull ABS sensor electrical connector out of holder.
Figure 2

Pull ABS sensor electrical connector out of holder. Disconnect by pressing release tabs and pulling apart. (green arrow) Be careful, these connectors become brittle over time and can crack if squeezed too hard.

Remove sensor wiring harness from strut.
Figure 3

Remove sensor wiring harness from strut. Pull the rubber grommet out of the metal bracket (green arrow), then open clip (yellow arrow) and remove wire.

Working at steering knuckle, remove ABS sensor 5mm Allen fastener.
Figure 4

Working at steering knuckle, remove ABS sensor 5mm Allen fastener. (green arrow) Pull ABS sensor out of steering knuckle. If it is stuck try lubricating it with penetrating oil.

If sensor still wonÂ't budge, lever out using a flathead screwdriver.
Figure 5

If sensor still won't budge, lever out using a flathead screwdriver. Lever close to the sensor and wiggle it out slowly. Install new sensor with a thin coating of Molykote Longterm 2 or similar grease to ABS sensor and housing. Install fastener and tighten. Then route wiring harness as it was before and reconnect at housing.

Rear ABS sensor:
Working at rear control arm (left side shown in photo), pull ABS sensor electrical connector out of plastic mount (green arrow).
Figure 6

Working at rear control arm (left side shown in photo), pull ABS sensor electrical connector out of plastic mount (green arrow).

Disconnect electrical connector by pressing release tab and pulling apart.
Figure 7

Disconnect electrical connector by pressing release tab and pulling apart. (green arrow) Be careful, these connectors become brittle over time and can crack if squeezed too hard.

Next you have to remove the ABS sensor wire form the plastic clips on the control arm.
Figure 8

Next you have to remove the ABS sensor wire form the plastic clips on the control arm. (green arrows). Spread the clips to open, then pull wire out.

Working at wheel bearing carrier, remove ABS sensor 5mm Allen fastener.
Figure 9

Working at wheel bearing carrier, remove ABS sensor 5mm Allen fastener. (green arrow) Pull ABS sensor out of steering knuckle. If it is stuck try lubricating it with penetrating oil.

If sensor does not slide out easily, lever out using a flathead screwdriver (green arrow).
Figure 10

If sensor does not slide out easily, lever out using a flathead screwdriver (green arrow). Lever close to the sensor and wiggle it out slowly.

The rear sensor has two mounting holes.
Figure 11

The rear sensor has two mounting holes. If swapping side to side for testing, you will use the opposite hole when mounting it to the other axle. Install new sensor with a thin coating of Molykote Longterm 2 or similar grease to ABS sensor and housing. Install fastener and tighten. Then route wiring harness as it was before and reconnect connector.

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Comments and Suggestions:
Mikey Comments: Nick - the sensor was super grimy but I did not clean the hub upon installing new sensor. I globed on some Permatex dielectric grease on new sensor and placed into same grimy hole. Should I have cleaned hub sensor receptacle ??
The ABS light did not come on until this repair - makes me suspicious!!!
Thanks Nick.
October 8, 2016
  Followup from the Pelican Staff: Most times I will clean the mounting surface for the sensor. If there is debris or rust, the sensor may lift up a bit, causing the signal to fail. - Nick at Pelican Parts  
Mikey Comments: Recent braking noise from front & then the ASC light came on. Replaced both wheel speed sensors today - terminal connector disintegrated but seemed to couple to new sensor ok. Both sensors were grimed up. Now ASC & ABS lights are illuminated.
Any Ideas???
Thanks
October 5, 2016
  Followup from the Pelican Staff: I would check if the repaired sensor signals are getting to the control module. May have a bad connection. - Nick at Pelican Parts  
Al Comments: My 1994 e36 ABS light has been coming on intermittently. I accessed the ABS module behind the glove box and tested the resistance. All checked OK. When the wheels were turned there was no voltage geneerated probably not turning the wheel fast enough.
I pulled the wheel speed senors and cleaned them. all except teh right rear which I could not budge and get out. I tried wedging a flat head screwdriver and got under the sensor but still could not move the sensor. I suspect it might be corroded and stuck. Any suggestions on removing it?
When I test drove the car, the ABS light is now on continuously so I suspect I damaged the right rear senor and or need to have the ABS reset.
October 3, 2016
  Followup from the Pelican Staff: twist the sensor using pliers to free it, then lever out using a flathead screwdriver. - Nick at Pelican Parts  
DON Comments: The DSC light on my dash came on. It IS THE ONLY light that is on. Would the fact that there are no other warning lights are on, eliminate any other causes? I cleaned all four of my wheel speed sensors,,,but didn't make the light go off. I was thinking about replacing all four of my sensors, but was afraid even that wouldn't solve the problem. HELP!
October 30, 2015
  Followup from the Pelican Staff: Could be anything in the ABS/ DSC system. Check the vehicle for fault codes. - Nick at Pelican Parts  
Jay Comments: I have an e36 318iM43 and recently the break pad wear sensor indicator started to show on even when my front break pads and discs are newreplaced 3 months ago then after 2 days of seeing this indicator the ABS indicator started to show on all the time in the instrument cluster. What could be the reason ?
July 2, 2015
  Followup from the Pelican Staff: Check if the wiring harnesses are loose and came in contact with the drive wheel. - Nick at Pelican Parts  
SCVOL75 Comments: I was removing the rear passenger abs wheel speed sensor by pressing release tabs and pulling apart. Unfortunately b/c the connector was brittle the tab on the male side broke. What's the fix? Replacement part?
September 21, 2014
  Followup from the Pelican Staff: You can replace the terminal end. Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need.
- Nick at Pelican Parts
 

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Page last updated: Wed 12/7/2016 02:06:43 AM