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Pelican Technical Article:

Brake Pad Sensor Testing

Nick Czerula

Time:

2 hours2 hrs

Tab:

$80

Talent:

***

Tools:

DVOM, jumper wires, floor jack, wheel chocks, jack stands, safety glasses, torque wrench

Applicable Models:

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

Parts Required:

Brake pad sensor

Hot Tip:

Stay clear of brake dust

Performance Gain:

Proper brake pad warning light function

Complementary Modification:

Replace brake pads

MINI R56 service brakes consist of hydraulic brake calipers and rotors, one at each wheel. When the brake pedal is pressed, brake fluid is forced out of the brake master cylinder and through the brake lines to each brake caliper. Pistons in the calipers push out and clamp the brake pads against the brake rotors (or discs), thus slowing down the vehicle. A vacuum assisted brake booster multiplies the braking force exerted by the driver at the brake pedal. The parking or emergency brake is integrated into the rear brake caliper. A pair of mechanically operated cables attached to the parking brake handle actuates parking brake levers inside the caliper.

You should check your brake pads every time you service your MINI. Replace your brake pads if the thickness is 2.4 mm (0.9 in.) or below. There are brake pad wear sensors that trigger a warning light when pads reach the minimum; however the sensor is only located on one brake pad per axle. This leaves three brake pads on each axle that are not monitored by the warning system. This is why periodic inspections are required. When replacing your brake pads, you can replace pads on one axle at a time. Have a new brake pad wear sensor handy. Even though the sensor may be reused, they become brittle and do not always fit tightly into the new pads when reused. On MINI R56 models, the brake pad wear sensor has been updated. It is now more dedicated and prone to breaking when removed. The sensor is no longer a simple wire circuit that is broken when pad wear hits the minimum. It is now a two-stage wear sensor. This provides the vehicle with more accurate brake pad monitoring. So if the sensor shows the slightest bit of wear, replace it.

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.

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.

In this article, I will show you how to check if your brake pad wear sensor is faulty.

Lift and support the axle you are replacing the brake pads on. See our tech article on jacking your vehicle.

Remove the wheel on the axle you are checking the sensor on.

The brake pad wear sensor on the front axle is located in the left front brake caliper (red arrow).
Figure 1

The brake pad wear sensor on the front axle is located in the left front brake caliper (red arrow). The rear sensor is located in the right rear caliper. I will show you how to test the front sensor; testing the rear is similar.

First, you will have to remove the pad wear sensor to inspect it.
Figure 2

First, you will have to remove the pad wear sensor to inspect it. Open the mount (red arrow) and remove the wire from the bleeder.

Next, remove the pad wear sensor from the brake pad using a pair of pliers (red arrow).
Figure 3

Next, remove the pad wear sensor from the brake pad using a pair of pliers (red arrow). Pull it straight out to remove it. If stuck, wiggle it from side to side slightly. Be careful. The sensor is fragile. If it breaks, replace it with a new one.

Inspect the sensor for wear.
Figure 4

Inspect the sensor for wear. The sensor shows about half worn on my subject vehicle (red arrow). If reused, this could prohibit the warning light from being reset. The green arrow points to a new sensor. Note how much more material is present.

To test the sensor we will have to access the electrical connector.
Figure 5

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).

Move to the bottom of the wheel well liner.
Figure 6

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.

Fold the wheel well liner (red arrow) away from the wheel well to expose the sensor connectors (green arrows).
Figure 7

Fold the wheel well liner (red arrow) away from the wheel well to expose the sensor connectors (green arrows). The rear sensor connector is located just ahead of the rear wheel well, above the small plastic splash shield.

Pull the white connector down and away from the mount.
Figure 8

Pull the white connector down and away from the mount. Disconnect the electrical connector by pressing the release tab and pulling it apart.

The sensor is a two-stage break pad wear sensor.
Figure 9

The sensor is a two-stage break pad wear sensor. When new the sensor resistance is below 5 ohms. When partially worn the sensor resistance changes to 470 ohms. When worn out, it is open or infinite resistance. Connect your DVOM (red arrow) across the sensor side terminals (yellow arrows). Set your DVOM to Ohms. Note the reading on my subject vehicle is about 485 ohms. The sensor is partially worn, so it is through the first stage of the sensor.

The sensor is a two-stage brake pad wear sensor.
Figure 10

The sensor is a two-stage brake pad wear sensor. When new the sensor resistance is below 5 ohms. This photo shows my DVOM connected to a new sensor. If your readings are correct at the sensor, but the wear indicator will not reset, inspect the wiring for the sensor to the junction box electronics (JBE). On my subject vehicle, the wear sensor wiring went into the JBE on terminals 33 yellow wire (front sensor), 9 black wire (front sensor), 10 yellow wire (rear sensor), and the 41 black wire (rear sensor). There could be an open or shorted wire. Double check the wiring for your vehicle to be sure it matches up.

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Comments and Suggestions:
Kingerbeerman Comments: I thinking had a rear sensor on the front, hence the reason for it not sitting properly...the front sensor clip is longer at the 90 degree then the rear.
June 10, 2016
  Followup from the Pelican Staff: Thanks for the follow up. - Nick at Pelican Parts  
Kingerbeerman Comments: Great article.
On my r56 these new sensors with the 90degree angle do not seem to clear the caliber to properly sit in the brake pad?
June 3, 2016
  Followup from the Pelican Staff: It should line up with the caliper. If not, the spring from the old sensor maybe stuck in the pad. - Nick at Pelican Parts  
jordan leavitt Comments: I really like how you said that, "When the brake pedal is pressed, brake fluid is forced out of the brake master cylinder and through the brake lines to each brake caliper." I had no idea that we needed to check our brake fluids for this reason. The other day my breaks went out and it turned out that I was out of brake fluid. What causes my brake fluid to run out?
February 4, 2016
  Followup from the Pelican Staff: You may have a fluid leak. - Nick at Pelican Parts  

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Page last updated: Fri 12/2/2016 02:50:47 AM