A wheel speed sensor is an electronic device that measures the rotational speed of a vehicle’s wheels. It is used to determine the speed of a vehicle. In this article’s step-by-step guide on how to test a wheel speed sensor using a multimeter?
The wheel speed sensors are crucial in controlling a vehicle’s brake system. The wheel speed sensors use non-contacting measurement principle and detect the rotational wheel speed of the vehicles”.
There are four ABS sensors, one on each wheel. Why? Because the traction control and abs need to read the speed of every wheel, and it is the sensor that does that.
How does the Wheel Speed Sensor work?
Usually, there will be a gear on the wheel’s axle and some sensor that can detect when one of the gear’s teeth comes close to the sensor. It causes a change in voltage.
If you graph these changes as a function of time, you will get something similar to the square wave. Using pretty sophisticated computers, we can count the number of rising edges on this graph in a given period.
2π (# of Pulses) = Radians
(Total # of Teeth)(Time in sec.) Second
Using the information from this equation, we can figure out exactly how fast our wheel is turning in radians per second which is an “Angular Velocity.”
2π (# of Pulses)(Radius in meters) = Meters
(Total # of Teeth) (Time in sec.) Second
If we also know the radius of our wheel, we can turn that number into something like miles per hour, which is a “Linear velocity.”
What if the Wheel Speed Sensor breaks?
Every wheel with ABS braking is subject to having fault crop up for ABS wheel speed sensor problems. This will result in the stability and traction control systems being offline and reduced functionalities such as hill start assist. These issues transcend make and model and can happen at any stage.
Tips for coping with faulty Wheel Speed Sensor:
- When the ABS warning light comes on, it’s best to scan the vehicle with diagnostic equipment. The good thing about wheel speed sensor codes is that the description generally tells you which sensor is experiencing trouble. Once you have this information, we can determine what kind of trouble it is, as not all reports are specific enough.
- Frequent and consistent dropout at different speeds indicates a problem with the reluctant ring, usually caused by corrosion, blockage or other damage. Check this to confirm.
- The other common fault is the wheel speed sensor with no signal or circuit fault. If this is the case, then we would expect a circuit fault.
- We also wouldn’t see a reading in the live data for that sensor. At this stage, we would locate the sensor ad check that it is receiving a 12-volt signal in the ground.
- While if the vehicle is not moving, in this condition that these feeds are not present, unplug the sensor itself and check for the voltages at the looming end once more. You have a faulty wheel speed sensor if they are present on this test. Replace this, and you should be good to go.
- On occasion, there are missing feds even with the sensor unplugged. Confirm that the ABS unit sends the correct output by performing the same tests at the module if accurate feeds are present here but not at the center end. Check your wiring, as there is more than likely high resistance in the loom that will need repair. However, if there are no voltage readings in your ABS module, it will need to be sent into the garage for a rebuild.
Wheel Speed Sensors checking with a multimeter
This article will help you properly troubleshoot and test an ABS wheel speed sensor. We use two tests when testing an ABS wheel speed sensor. The first test will be looking at will be the ABS wheel speed sensor resistance test.
ABS Wheel Speed Sensor Resistance Test:
This test is used when you have a fault code indicating a faulty wheel speed sensor with an issue such as a short or open circuit. To perform this test, we will look at the wheel speed sensor that connects to an extension cable route to the ECU.
We want to begin by disconnecting the relevant sensor and checking for corrosion. Next, we will measure the resistance between the two pins in the sensor connection housing.
We will do this using an Ohms meter. The reading on the ohms meter should be between 980 and 2350 ohms. If the sensor is outside this range, replace the cable. If the sensor readings are within the specific range, connect the sensor to the sensor extension and continue checking the harness.
ABS Wheel Speed Sensor Voltage Test:
Now we will look at performing the voltage check on the sensor cable first. Let’s go where the sensor cable connects to the sensor extension cable. Remove the yellow sensor extension clip. Once you take the buckle off, disconnect the sensor cable.
Be sure to take a look for any corrosion that may be present on either side of the sensor cable or the sensor extension cable. To perform the voltage check, you will need your multimeter.
You will set it to check AC volts. Then, check the pins in the wheel speed sensor harness with the multimeter probes. While doing this, spin the wheel that the wheel speed sensor is connected to; you need to spin the wheel at a rate of about 1 revolution every 2 seconds, with the wheel spinning at the desired rotation level. Check the readings on the multimeter.
The multimeter should be reading at least 200 millivolts (0.2 VA). If this is not the case, push in the sensor until it touches the exciter ring and performs this test again.
If this still does not fix the problem, you may need to check the wheel bearings, play-check the toothed wheel for any damage, and check that the wheel has the same number of teeth at each wheel end. This may mean you must ensure the correct tire size is used with the right tooth wheel.