The variable-reluctance magnetic sensor has a permanent magnet pickup core and coil surrounding the magnet. These are typically found on pre-2003 vehicles. The sensor is mounted at a specific gap from a notch and tooth reluctor ring.
What kind of sensor is a wheel speed sensor?
Currently, two types of wheel speed sensors are in use: magnetic inductive (passive) and magneto resistive (active) . Passive sensors have been around since the early days of the anti-lock brake system (ABS). These are the sensors that function on the generator principle.
What is a passive wheel speed sensor?
The passive speed sensor creates its own AC signal that changes frequency with wheel speed . ... This signal is only present while the wheel is turning at a rate fast enough to create the AC signal. Passive wheel speed sensors generally do not read at or below 2 mph coming from a dead stop.
Is a wheel speed sensor analog or digital?
Unlike the passive sensor's AC output signal, changes in the electromagnetic field produced by the toothed tone ring passing the wheel speed sensor cause the active wheel speed sensor to produce a DC voltage signal. It's a digital high/low voltage , unlike the analog voltage signal produced by a passive sensor.
Is a wheel speed sensor an ABS sensor?
An anti-lock brake sensor or ABS sensor is a type of tachometer that measures the rotational speed of a wheel and passes it to the car's Engine Control Module (ECM). The ABS sensor is also called the wheel speed sensor or ABS brake sensor.
What is the difference between an active and a passive wheel speed sensor?
A passive sensor creates an AC signal that changes frequency as the wheel changes speed . ... An active wheel speed sensor creates a digital signal. This type of digital wheel speed sensor uses a hall effect or a variable reluctance signal with a square wave pattern. The sensor may have two or three wires.
Can you drive with a bad wheel speed sensor?
That is why in general, it is unsafe to drive a vehicle with a broken wheel speed sensor . If the wheel speed sensor becomes damaged or wears out, initially you probably won't notice much difference in the way your car performs if your ABS light comes on unless you are driving on slippery pavement.
What type of signal does a passive speed sensor produce?
Passive sensors output a sinusoidal signal which grows in magnitude and frequency with wheel speed. A variation of the passive sensor does not have a magnet backing it, but rather a tone wheel which consists of alternating magnetic poles produce the alternating voltage.
How do you test a passive wheel speed sensor?
When testing a passive WSS, the positive lead of the meter should be connected to the signal wire . The negative should go to the ground or a chassis ground depending on the test you are doing. The sensor and/or harness should be disconnected from the circuit so you are not measuring resistance in the ABS unit.
Why are the wires leading to some wheel speed sensors twisted?
The traction control module is designed to work with inductive ABS sensors. These have two wires from each sensor. ... The pair of wires for each wheel should be twisted – this reduces the effect of any interference .
Is wheel speed sensor Hall effect?
A Hall effect wheel speed sensor uses this technology to produce a square wave output in response to the magnetic field disturbances caused by a rotating pulse wheel mounted around a hub or driveshaft. Hall effect wheel speed sensors require power to operate; hence they are referred to as active sensors.
How much is a wheel speed sensor?
The average cost for a Wheel Speed Sensor Replacement is between $209 and $254 but can vary from car to car.
How many wheel speed sensors are on a car?
Modern vehicles have four wheel speed sensors : two front wheel speed sensors and two rear wheel speed sensors. That is, each wheel of your car has a wheel speed sensor.
What causes a wheel speed sensor to go bad?
As soon as the wheel turns, the cover is knocked off by the tone wheel teeth. It is common for dirt to accumulate on the sensor which inhibits its ability to generate a signal. ... Although sensors can go bad, the most common problem is faulty wiring or corroded electrical connections .
What causes ABS sensor to fail?
What are the common causes of failure? Typically these sensors will fail as a result of clogging from metallic debris, brake dust or dirt due to exposure to the harsh elements .
Can you clean a wheel speed sensor?
With the sensor free, take your rag and wipe the sensor until it's clean . I prefer not to use any chemicals on the sensor to avoid potential problems. If, however, the sensor is really grungy, use a mild soapy solution and rinse well. The ABS sensors are precision instruments in a crude environment.
