ABS sensor Subaru Forester

Subaru Forester Front Wheel Speed Sensor video shows the speed sensor location on a Subaru Forester.

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ABS Wheel Speed Sensors Diagnosis

When a wheel speed sensor (WSS) fails or there's a problem in the sensor's wiring circuit, it usually disables the ABS system and causes the ABS warning light to come on. Loss of a wheel speed signal is a serious problem because the ABS module needs accurate input from all its sensors to determine whether or not a wheel is locking up. Without this vital information, the ABS system can't do its thing.

Wheel speed sensors produce an alternating current (AC) output voltage that varies in frequency and amplitude with wheel speed. The faster the wheel turns, the greater the frequency and amplitude of the sensor's output signal. The strength of the signal can be affected by resistance in the sensor, resistance in the wiring and connectors, metallic debris on the end of the sensor, and the air gap between the sensor and tone ring mounted on the axle, hub, brake rotor, drum or CV joint.

A narrow air gap is usually necessary to induce a strong signal in the sensor's magnetic windings. Air gaps typically range from .016 in. to as much as .050 in. (0.40 to 1.3 mm) depending on the application. If the ABS warning light is on and you find a code for a wheel speed sensor (and the sensor is adjustable), the problem may be nothing more than too wide an air gap. Use a brass or nonmagnetic feeler gauge set the gap to the factory recommended specs.

Variations in the air gap can also cause fluctuations in the sensor's output signal. These may be caused by bad wheel bearings or missing, broken or chipped teeth on a tone ring. Even minor damage to the tone ring that's nearly impossible to see can sometimes cause a problem. One equipment supplier makes a test bench with a magnetic pickup and oscilloscope to check tone rings on remanufactured FWD axle shafts. The setup simulates the signal produced in a wheel speed sensor. Tests have shown that a variation in height of only about .010 inch on a single tooth can cause a noticeable fluctuation in the sensor's output signal!

WHEEL SPEED SENSOR CHECKS

One way to check a suspicious wheel speed sensor is to measure its output voltage. One way to do this is to plug a breakout box into the ABS module's wiring harness and attach the test leads from a digital volt ohm meter (DVOM) to the appropriate pins for the WSS circuit.

A good wheel speed sensor will generally produce an alternating current (AC) voltage reading of 50 to 700 MV when the wheel is spun by hand at about one revolution per second. Refer to a shop manual for the sensor's exact voltage specifications.

A low voltage reading or no reading calls for a direct measurement of the resistance in the WSS circuit (with the key off). This should be done through the breakout box to check the entire circuit. A good wheel speed sensor and circuit will typically have a resistance of 800 to 1400 ohms (specs vary, so refer to a manual for the exact numbers).

If the sensor circuit has too much resistance, reads open or is shorted (little or no resistance), measure the resistance across the sensor itself. If the sensor itself reads within specs, the problem is in the wiring or connectors. If not, then you have identified a bad sensor that needs to be replaced.

SCOPE CHECKS

This isn't something a do-it-yourselfer can do, but a dynamic check of a sensor's output with an oscilloscope is one of the best ways to analyze the performance of a wheel speed sensor. The waveform on the scope can reveal problems that might not be detectable by other means. A damaged tooth on a tone ring, for example, may not produce a noticeable change in the sensor's output voltage if you are reading the output with a DVOM or an analog voltmeter. But it may distort the waveform enough to upset the operation of the ABS system and set a fault code.

The scope connection can either be made through the breakout box or hooked directly to the wheel speed sensor. A "good" scope pattern should show a sine wave alternating current pattern that changes both in frequency and amplitude with wheel speed. Spinning the wheel faster should cause both frequency and amplitude to increase.

If the scope pattern is flattened (diminished amplitude) or is erratic, it usually indicates a weak signal caused by an excessively wide air gap between the tip of the sensor and its ring, or a buildup of metallic debris on the end of the sensor. A weak signal can also be caused by internal resistance in the sensor or its wiring circuit, or loose or corroded wiring connectors.

Damaged or missing teeth on the sensor ring will show up as flat spots or gaps in the sine wave pattern. A bent axle or hub will produce an undulating pattern that changes as the strength of the sensor signal changes with every revolution.

Something else that can be detected with a scope is mismatched parts. If the brake rotor, CV joint or axle has been recently replaced, and the new part did not have the correct number of teeth on the sensor ring, it will cause the sensor to read fast or slow compared to the others and set a fault code. Comparing the sensor patterns side-to-side will reveal this kind of problem.

ACTIVE WHEEL SPEED SENSORS

On some late model vehicles (such as Jeep, Chrysler and others), a different type of wheel speed sensor is used. Active wheel speed sensors (also called Magnetic Resistance Element or MRE sensors) use a Hall effect sensor to generate a digital speed signal with a square wave pattern. This type of sensor can generate a more accurate wheel speed signal at low speeds (down to 1 mph) than a magnetic WSS. It can also tell if the wheel is rotating forwards of backwards.

With this type of sensor, the body control module or ABS module provides a reference voltage to power the sensor. Inside the sensor is a pair of pickups that detect changes in the magnetic field of a magnetic ring on the wheel bearing. The ring has permanent magnets that alternate north and south poles. When the wheel rotates, the changing magnetic field produces a small electric current in the sensor pole pieces. The internal electronics in the sensor then converts the voltages into a digital output signal that goes back to the control module. The voltage, amperage and frequency of the return signal is proportional to wheel speed.
Troubleshooting an Active Wheel Speed Sensor

Some of these sensors have three wires while others have only two. On the three-wire sensors, one wire is for power, one for ground and one for the return signal. On the two-wire sensors, one is the power and the other is ground. The return signal travels back to the module over the power supply wire. On Jeep and Chrysler applications with two-wire sensors, the return signal is a 7 to 14 milliamp square wave signal. You should be able to see the signal by SLOWLY rotating the wheel while backprobing the return circuit with a multimeter set to read milliamps or a digital scope. No signal means a bad sensor or wiring fault.

NOTE: Active wheel speed sensors cannot be accurately tested by measuring resistance across the sensor's terminals. You have to look for a good return signal from the sensor while it is receiving power from the control module or a 12-volt battery, and while the wheel is turning.

If you have a scan tool that can read ABS codes (not just engine/transmission codes), you can also check for wheel speed sensor codes on your vehicle. A scan tool that can also display the speed readings from each sensor while driving can also help you pinpoint which sensor is bad. All the sensors should read the same while driving straight ahead. If one is showing a different speed (faster or slower than the others), there is a problem in that sensor circuit (either a bad sensor, a faulty magnetic sensor ring, or a wiring fault). The sensor may be misreading wheel speed if the magnetic ring on the wheel bearing is cracked or damaged.

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ABS Sensor Ford F-150

Ford F150 ABS sensor test & replacement video. Watch how to testing and replacing an ABS sensor on a 2002 Ford F-150 FX4 truck. ABS sensor replacement on front driver side. Part# 970-074 Dorman.

How to Change an ABS Wheel Sensor. Ford Taurus

ALS114 Rear Wheel ABS Sensor for Ford Taurus & Mercury Sable1990-1995

The anti-lock braking system (ABS) on the Ford Taurus uses a wheel sensor to monitor the wheel speed on each wheel. The ABS controller uses this information to prevent the brakes from locking during an emergency stop. If the ABS warning light comes on, it may indicate the wheel sensor has become clogged with metallic debris such as brake dust.


Things You'll Need:
New ABS wheel sensor
Socket wrench set
Thread-locking compound
Torque wrench


Determine which ABS wheel sensor your Ford Taurus will need. You'll want to be sure the new wheel sensor is compatible with your make and model of Taurus. All versions of the Taurus have been equipped with ABS since its debut in 1999.


Unhook the negative battery cable with a socket wrench and raise the vehicle.


Unplug the electrical connection from the front wheel speed sensor located in the engine compartment. Remove the plastic studs for the splash shield on the front fender.


Detach the grommets for the wheel speed sensor cable at the rail bracket and retainer on the strut housing. Remove the wheel speed sensor retaining bolt with a socket wrench and separate the sensor from the steering knuckle.


Disconnect the wheel speed sensor on rear wheels from the electrical cable in the center of the cross member. Release the retaining clips from the suspension arm and cross member.


Remove the wheel speed sensor retaining bolt with a socket wrench. This bolt attaches to the brake adapter on station wagons and the brake spindle on sedans. Separate the wheel speed sensor assembly from the vehicle.


Install the new wheel speed sensor by reversing the removal procedure. Apply thread-locking compound to the retaining bolt and use a torque wrench tighten it to between 90 and 120 for front wheel sensors. Torque the mounting bolts for rear wheel speed sensors to between 62 and 98 in. lbs.

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ABS sensors Chrysler Town and Country 2008 Testing

Testing the ABS sensors on a 2008 Chrysler Town and Country video. Testing the signals on an ABS sensor on a Chrysler Town Country 2008. These are new sensors that are working properly. The old sensors were replaced due to codes C1020 and C102B. The voltage supply is at 12 volts and that is the wire where the speed sensor signal is seen

How to replace abs sensor Chrysler Pacifica

REMOVAL
1. Access and remove rear hub and bearing from vehicle.
2. Remove screw fastening speed sensor head to hub and bearing. See Fig. 4

Fig. 4: Rear Hub And Bearing With Wheel Speed Sensor

1. SCREW
2. WHEEL SPEED SENSOR
3. HUB AND BEARING

CAUTION: Prior to removal, clean area around sensor head to help prevent contaminants from entering bearing when sensor head is removed.

3. Remove wheel speed sensor from hub and bearing.

INSTALLATION
1. Apply bearing grease (supplied with part) to sensor head shaft and O-ring.
2. Push sensor head into mounting hole in hub and bearing and align mounting screw hole.
3. Install NEW mounting screw. See Fig. 4. Tighten mounting screw to 20 N.m (15 ft. lbs.) torque.
4. Install hub and bearing with wheel speed sensor as well as all com ponents necessary to access it.
5. Road test vehicle to ensure proper operation of the base brakes and ABS

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Buick ABS Sensors Cleaning

The Mercury Mountaineer features a anti-lock brake system for the rear wheels only. This system uses a sensor to measure the rotational speed of each wheel. The system adjusts the amount of braking power each wheel receives when the brake pedal is depressed. This prevents the wheels from locking and helps to provide stable deceleration. The anti-lock brake sensor on your Mountaineer can fail, requiring replacement. Replacing a rear anti-lock brake sensor is a repair job that most do-it-yourself mechanics can complete in under an hour.


Things You'll Need:
Adjustable wrench
Socket wrench


Disconnect the negative battery cable with an adjustable wrench.


Clean the axle housing around the sensor with a rag or shop towel. Disconnect the electrical harness from the sensor, located on the axle housing.


Remove the bolt from the sensor with a socket wrench and remove the sensor from the axle.


Lubricate the new sensor with a small amount of engine oil. Install the new sensor using the mounting bolt and tighten it with a socket wrench.


Connect the electrical connector to the sensor.


Connect the negative battery cable with an adjustable wrench.

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Toyota Corolla ABS sensor replacement

Video how to change ABS brake sensor Toyota Corolla. Years 2000-2010

Rear ABS Sensor Changing on a Mercury Mountaineer

The Mercury Mountaineer features a anti-lock brake system for the rear wheels only. This system uses a sensor to measure the rotational speed of each wheel. The system adjusts the amount of braking power each wheel receives when the brake pedal is depressed. This prevents the wheels from locking and helps to provide stable deceleration. The anti-lock brake sensor on your Mountaineer can fail, requiring replacement. Replacing a rear anti-lock brake sensor is a repair job that most do-it-yourself mechanics can complete in under an hour.


Things You'll Need:
Adjustable wrench
Socket wrench


Disconnect the negative battery cable with an adjustable wrench.


Clean the axle housing around the sensor with a rag or shop towel. Disconnect the electrical harness from the sensor, located on the axle housing.


Remove the bolt from the sensor with a socket wrench and remove the sensor from the axle.


Lubricate the new sensor with a small amount of engine oil. Install the new sensor using the mounting bolt and tighten it with a socket wrench.


Connect the electrical connector to the sensor.


Connect the negative battery cable with an adjustable wrench.

Source

ABS Speed Sensor Symptoms

The anti-lock brake (ABS) system uses sensors that send data to the ABS module which will activate it during wheel lock. These sensor mechanisms are installed at the wheel, and is usually made up of two components. There will be a reluctor wheel or tone ring seated on the axle which will spin with the wheel, and either a magnetic or hall effect sensor which works together to send data to the ABS control module. Over time, the reluctor wheel may become dirty or damaged to the point where it can no longer provide a consistent reading, or the magnetic/hall effect sensor may fail. When either of these components fail, the ABS system will not function properly and will require service.

Different cars will have different ABS sensor configurations. Older vehicles may have only one or two sensors on the entire vehicle, while most new ones will have one at each wheel. Individual sensors at each wheel allow for more precise readings and operation, however, it does leave the system prone to more problems. When an ABS sensor fails, there are usually a few warning signs that will warn you that there is a problem.
The ABS Light comes on

The most obvious sign of a problem with the ABS system is that the ABS Light will come on. The ABS Light is the equivalent of the Check Engine Light, except only for the ABS system. When the light is illuminated, this is usually the first sign that will be displayed indicating that there may be a problem with the ABS system, and perhaps an issue with one of the system’s sensors.
Decreased stopping time

During heavy braking conditions the ABS system should automatically activate to aid in slowing down the vehicle, and traction loss and skidding should be minimal. While we should try to practice regular driving habits that avoid heavy braking situations, if you do notice that the vehicle is taking longer to stop under heavy braking situations, or is experiencing traction loss and skidding, then that may be an indicator of there being a problem with the system. The ABS system is typically made up of only a few components - the module and the sensors - so a problem in its operation will either be with the module or the sensors.
Less stability under icy or wet driving conditions

Over time, most drivers will become familiar with how their vehicle handles under certain conditions, including slippery conditions, such as driving on wet or icy roads. A properly functioning ABS system will minimize any sort of traction loss, especially under wet and icy conditions. If when driving under wet or icy roads you experience any sort of tire slipping or loss of traction for more than a brief moment when stopping or taking off, then the ABS system may not be functioning correctly. This is typically due to either a problem with the module, or more likely, a problem with the sensors.

If your ABS Light comes on, or you suspect you may be having a problem with one or more of the ABS sensors, have the vehicle inspected by a professional technician, such as one from YourMechanic, to determine the exact nature of the problem, and if any repairs need to be made. They will also be able to replace your ABS Sensors if needed.

Source

How to replace ABS sensor Honda Accord

"How To Install Replace ABS Sensor and Harness Honda Accord Odyssey Acura CL" shows you how to repair, install, fix, change or replace a bad, broke, cut or damaged ABS harness on a 1995 Honda Accord. This procedure is similar on all 94, 95, 96, and 97 Honda Accord, 95 to 98 Honda Odyssey, and 97 to 99 Acura CL. A cut or damage ABS Sensor can cause your ABS light to come on and your ABS to work incorrectly.

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How to change abs sensor Honda Civic

ABS Sensor Diagnostics and Replacement Honda video demonstrates how to test and change an ABS wheel speed sensor on a Honda.

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ABS sensor troubleshooting

Standard motor products als1 driveline abs sensor

The anti-lock braking system is an electrical system that prevents your brakes from locking up during braking. Anti-lock braking systems (ABS) prevent fishtailing and other unexpected dangers when driving in bad weather conditions. When the ABS sensor comes on in the car, you may have an issue with the ABS system. Knowing how to troubleshoot the ABS sensor problem may prevent a nasty accident from a faulty ABS system. You may even find that the ABS sensor is firing without a proper issue behind it.


Things You'll Need

• Fuse
• Voltmeter

Inspect the brake fluid level of the car by lifting out the brake fluid dipstick and checking the level on the stick. Fill the brake fluid if necessary.


Listen for grinding noises from the brakes. This indicates a problem with the brake cylinders or pads, and not an issue with the ABS. Increased pressure needed on the brake pedal for regular braking also indicates an issue.


Turn the ignition key "On" and "Off" to turn on the car's electrical system to see if the ABS light resets. If not, further troubleshooting is needed.


Check the fuse for your ABS unit. The fuse is inside the fuse panel inside the car. Check the resistance level of the fuse and the fuse panel using a voltmeter. Set the voltmeter to the resistance setting indicated in your car manual, and check the fuse port by inserting the probes from the voltmeter into the port. Check the resistance value against the value in your manual.


Unplug the main harness for the ABS system controller, and plug it back in to reset the system. If the warning light still comes on, take your car to a professional mechanic.


Have the mechanic run an ABS controller diagnostic. This costs less than $100, and tells you where to look by giving you an error code that indicates the source of the problem

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