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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:

$150

Talent:

****

Tools:

Pliers, 5mm Allen bit, 8mm socket, floor jack, jack stands, wheel chocks, safety glasses, torque wrench

Applicable Models:

R56 MINI Cooper Hatchback (2007-11)
R56 MINI Cooper S Hatchback (2007-11)

Parts Required:

ABS wheel speed sensor, Molykote Longterm 2 grease

Hot Tip:

Check for fault codes before replacing

Performance Gain:

Repair faulty ABS sensor

Complementary Modification:

Properly route wiring and use new clips if needed

The ABS wheel speed sensor monitors road wheel movement and sends an electronic signal to the ABS / DSC module. This signal is used to calculate road wheel speed to help with ABS braking and stability control features. Sensors are bolted to each wheel hub and are therefore susceptible to damage from impacts, road grime and brake dust.

MINI R56 models utilize a magneto resistive style wheel speed sensor. This style of sensor allows accurate wheel speed reporting as soon as the wheel moves, unlike older style inductive sensors that required a speed of about 7 MPH to start working. This allows greater dynamic system control at lower vehicle speeds. This sensor type creates a high to low signal. The low signal is just above 9 volts, and the high about 12 volts. It is important to use a lab scope when testing these sensors, because this is the best way to display the digital signal created by the sensor.

When an ABS wheel speed sensor fails, the ABS / DSC module looses 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 / DSC warning light will illuminate. You will 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 / DSC warning light. Be sure to scan and read the fault codes before replacing parts.

You can use a scan tool while monitoring wheel speed signals to check for a slower or faster wheel. This can help to pinpoint a faulty sensor. Compare all four-wheel speed signals together. Look for one that doesn't match the others. To see how to test individual sensors and related fault codes, see our tech article on ABS wheel speed sensor testing.

In this tech article, I will go over how to replace the front and rear wheel speed sensors.

Remember that your car may have been serviced before and had parts 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.

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. Never work on your vehicle if you feel the task is beyond your ability.

Our vehicle may vary slightly from yours as models do change and evolve, as they grow older. 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 the ABS sensor on. See our tech article on lifting your vehicle safely.

A faulty wheel speed sensor can set multiple brake warning lights (green arrows).
Figure 1

A faulty wheel speed sensor can set multiple brake warning lights (green arrows). It is important to check for fault codes using a MINI scan tool to identify the problem sensor.

It is important to check for fault codes using a MINI scan tool to identify the problem sensor.
Figure 2

It is important to check for fault codes using a MINI scan tool to identify the problem sensor. My subject vehicle has a fault code for the right rear and left front sensors -- one fault code pertaining to the circuit and one to the signal. This helps to identify the problem sensors. To see how to test the individual sensors and related fault codes, see our tech article on ABS wheel speed sensor testing.

Front sensor: The front wheel speed sensor is mounted in the spindle (red arrow), at the top.
Figure 3

Front sensor: The front wheel speed sensor is mounted in the spindle (red arrow), at the top.

Front sensor: To test the sensor we will have to access the electrical connector.
Figure 4

Front sensor: To test the sensor we will have to access the electrical connector. Working in the front wheel well, remove the Phillips head plastic screw (red arrow). Then remove the expanding anchor (inset).

Front sensor: Move to the bottom of the wheel well liner.
Figure 5

Front sensor: Move to the bottom of the wheel well liner. Remove the Phillips head plastic screw (red arrow). Then remove the expanding anchor. The green arrow points to the previously removed plastic screw and anchor.

Front sensor: Fold the wheel well liner (red arrow) away from the wheel well to expose the sensor connector (green arrow).
Figure 6

Front sensor: Fold the wheel well liner (red arrow) away from the wheel well to expose the sensor connector (green arrow).

Front sensor: Pull the ABS sensor electrical connector out of the holder.
Figure 7

Front sensor: Pull the ABS sensor electrical connector out of the holder. Disconnect it by pressing the release tab (red arrow) and pulling it apart. Be careful; these connectors become brittle over time and can crack if squeezed too hard. 

Front sensor: Follow the sensor wire to the mount at the body.
Figure 8

Front sensor: Follow the sensor wire to the mount at the body. Then squeeze the retaining tabs (red arrow) together and pull the wire out of the bracket (inset).

Front sensor: Unclip the brake pad wear sensor wiring from the wheel speed sensor (red arrow).
Figure 9

Front sensor: Unclip the brake pad wear sensor wiring from the wheel speed sensor (red arrow).

Front sensor: Remove the sensor wiring harness from the mounts (red arrows) on the strut by pulling them straight out.
Figure 10

Front sensor: Remove the sensor wiring harness from the mounts (red arrows) on the strut by pulling them straight out.

Front sensor: Working at the steering knuckle, remove the ABS sensor 5mm Allen fastener (red arrow).
Figure 11

Front sensor: Working at the steering knuckle, remove the ABS sensor 5mm Allen fastener (red arrow).

Front sensor: Pull the ABS sensor out of the steering knuckle.
Figure 12

Front sensor: Pull the ABS sensor out of the steering knuckle. Then remove it from the vehicle.

Front sensor: If the sensor does not slide out easily, pull it out using a pair of pliers.
Figure 13

Front sensor: If the sensor does not slide out easily, pull it out using a pair of pliers. Pull up and wiggle it out slowly. Install a new sensor with a thin coating of Molykote Longterm 2 or similar grease to the ABS sensor and housing. Install the fastener and tighten. Then route the wiring harness as it was before and reconnect it at the mount. Reassemble the wheel well liner.

Rear sensor: The rear sensor in mounted in the rear swing arm behind the strut.
Figure 14

Rear sensor: The rear sensor in mounted in the rear swing arm behind the strut. Start by removing the 8mm fastener (red arrow).

Rear sensor: Remove the 8mm fastener.
Figure 15

Rear sensor: Remove the 8mm fastener. I like to use a four-inch extension on my 1/4-inch drive ratchet.

Rear sensor: Pull the ABS sensor out of the steering knuckle.
Figure 16

Rear sensor: Pull the ABS sensor out of the steering knuckle. Then remove it from the vehicle. If the sensor does not slide out easily, pull it out using a pair of pliers. Pull and wiggle it out slowly.

Rear sensor: Remove the sensor wiring harness from the mounts (red arrows) on the strut and body by pulling them straight out.
Figure 17

Rear sensor: Remove the sensor wiring harness from the mounts (red arrows) on the strut and body by pulling them straight out.

Rear sensor: Follow the sensor wiring to the body in front of the rear wheel well.
Figure 18

Rear sensor: Follow the sensor wiring to the body in front of the rear wheel well. Pull down on the small plastic shield (red arrow) for easier access. Pull the connector (green arrow) out of the holder. Then disconnect it by pressing the release tab (yellow arrow) and pulling it apart. Be careful. These connectors become brittle over time and can crack if squeezed too hard. Install a new sensor with a thin coating of Molykote Longterm 2 or similar grease to the ABS sensor and housing. Install the fastener and tighten. Then route the wiring harness as it was before and reconnect it at the mount.

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