Red cars image by Catabu from Fotolia.com Most vehicles today have anti-lock brakes. The wheel speed sensor works in conjunction with the anti-lock brake system by interpreting the rotational speed of the tire through a magnetic signal. The wheel speed sensor can tell if a tire stops rotating or locks up, and it sends that signal to the anti-lock brake system so it can relieve pressure and allow the wheel to turn. Wheel speed sensors mount on each wheel to record individual wheel speeds, and activate a signal after the car is traveling at approximately 3 to 5 mph. Since the signal sends an electronic pulse, you can test the wheel speed sensor with a multimeter.

Step 1

Park the vehicle and turn off the engine with the transmission in «Park» or neutral. Set the emergency brake.

Step 2

Locate your vehicle’s main fuse block. Refer to your owner’s manual for its location. Look in the engine compartment, driver’s side kick panel or in the glove box. Remove the fuse block lid and locate the ABS fuse. Make sure the filament inside the fuse appears intact; replace if necessary.

Step 3

Loosen the lugs on all four wheels with a tire iron — do not remove the lug nuts. Lift the front of the vehicle with a floor jack and place two jack stands under the frame near each wheel. Lift and support the rear of the vehicle in the same way. Finish removing all the lug nuts with the tire iron, then set the wheels aside.

Step 4

Release the emergency brake and set the gearshift in neutral. Sit down underneath the front wheel well and look for a wire coming from the wheel speed sensor mounted on the rotor, CV joint or wheel hub. It will look like a small plastic box. The wire will lead up through the fender well. Disconnect the wire at the jack by pulling it apart with your fingers. Look at the two-pin connector.

Step 5

Set a multimeter to measure resistance (ohms). Place each probe of the multimeter on each pin inside the connector. Connect it to the end of the wire that comes from the sensor. Note the ohm reading on the gauge. Have an assistant manually rotate the wheel hub as fast as he can while you hold the probes in place. See if the ohm number changes with the spin of the wheel. Any change in ohms indicates a good connection to the sensor. No change indicates a broken or shorted wheel sensor wire.

Step 6

Switch the multimeter setting to the volts scale, 10 volts maximum. Insert a flying lead between the two wire connections. Flying leads have extensions that plug into the female side and the opposite male side, with some bare metal exposed, so you can probe both wire sides with the jack connected. Place one lead from the multimeter onto one flying lead, and the other probe to the other flying lead.

Step 7

Have your assistant turn the ignition key to the «On» position. Look at the voltage reading on the gauge. Normal voltage will be between +5 or +12 volts, depending upon the ABS specifications. Refer to your owner’s manual for the exact number. With the key still on, have your assistant rotate the wheel hub again. If you see a voltage change, the wheel speed sensor functions properly. If the voltage does not change you have defective sensor.

Step 8

Check the rest of the wheel speed sensors on each wheel with this same procedure. Any difference in the ohm or voltage readings on a wheel will indicate either a wire break, short or a defective sensor. Be certain to reconnect all the wheel speed sensor jacks when finished. Mount the wheels on the vehicle and use a tire iron to partially tighten all the lug nuts. Use the floor jack to lift the vehicle and remove the jack stands. Use a torque wrench to tighten all the lug nuts to manufacturer’s specifications. References Tips

• All of the wheels on your vehicle must be the same size diameter and profile to get consistent and accurate readings from your wheel speed sensor. If the tires are mismatched, each reading for each tire might differ and confuse the ABS signal.

Things You’ll Need

• Owner’s repair manual
• Floor jack
• Jack stands
• Tire iron
• Assistant
• Digital Multimeter
• Flying leads
• Torque wrench

Writer Bio Chris Stevenson has been writing since 1988. His automotive vocation has spanned more than 35 years and he authored the auto repair manual «Auto Repair Shams and Scams» in 1990. Stevenson holds a P.D.S Toyota certificate, ASE brake certification, Clean Air Act certification and a California smog license.

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The Drive and its partners may earn a commission if you purchase a product through one of our links. Read more. So your car’s transmission is acting up or throwing a heart-stopping fault code and you want to find out if the speed sensors are causing it? Fabulous. Your car’s transmission speed sensors are vital to its powertrain operation. Most modern cars have two transmission speed sensors, one at the input shaft and another at the output shaft. These sensors work in tandem to send the powertrain control module (i.e., the computer that manages the engine and transmission) the speed difference between the engine crankshaft and the transmission output shaft, and thus, the gear ratio. That data, along with data from other sensors around the car, is used to set shift points, adjust engine calibrations, and even manage cruise control. If those sensors aren’t working properly, the transmission may shift roughly or sluggishly, cruise control may not work, or the speedometer may malfunction. Diagnosing a faulty transmission speed sensor is pretty straightforward, as is replacing it, but to diagnose a problem fully, you’ll need to be comfortable using a multimeter to check voltage. If not, take your car to a qualified mechanic for a proper once-over. The Drive’s crack How-To team is here to help you diagnose and fix your transmission speed sensor issues, and get back on the road.

Basics

Estimated Time Needed: Half-hour Skill Level: Intermediate Vehicle System: Transmission Depositphotos

Safety

Working on your car can be dirty, especially when you’re working with surfaces you’ve never bothered to clean before. It can also be dangerous as liquids can be scaldingly hot and tires could fall on your toes. So here’s what you’ll need to ensure you keep your jeans, shirt, and skin spotless, and your bones fully intact.

• Mechanic gloves.
• Long-sleeve shirt to protect your arms.
• Eye protection.

Organizing your tools and gear so everything is easily reachable will save precious minutes waiting for your handy-dandy child or four-legged helper to bring you the sandpaper or blowtorch. (You won’t need a blowtorch for this job. Please don’t have your kid hand you a blowtorch—Ed.) You’ll also need a flat workspace, such as a garage floor, driveway, or street parking. Check your local laws to make sure you’re not violating any codes when using the street. Depositphotos

Everything You’ll Need

We’re not psychic, nor are we snooping through your toolbox or garage, so here’s what you’ll need to get the job done.

Tool List

• Pliers
• Multimeter
• Socket wrench

Parts List

• New transmission speed sensors (if applicable)

Depositphotos

Here’s How to Test Your Transmission Speed Sensors

Let’s do this! Testing Transmission Speed Sensors

1. Using an OBD2 scanner, check to see if there are any error codes related to the transmission speed sensor.
2. If there are, there’s your problem. The part will need to be replaced.
3. If there aren’t any codes, or if your car is from the Regan years, you’ll need to physically test the sensor.
4. For better clearance, lift up the front end of your vehicle.
5. Locate the transmission speed sensors, they’ll be near the front and rear of the transmission housing. Consult the repair manual for your car.
6. Place bucket or oil drain pan underneath the sensor, there will be some oil that drains out.
7. Disconnect the sensor from the housing on the transmission, as indicated in the repair manual for your car.
8. Disconnect the sensor’s wire coupling.
9. Turn the key to the ignition on, but engine off, position (one key click past Accessory)
10. Using the multimeter’s voltmeter connect the probes to the ground and reference wires in the connector.
11. If no voltage is received, the sensor is faulty.
12. If voltage is received, you may need to have the car diagnosed by a qualified tech.

Replacing Your Transmission Speed Sensors

1. Having found the sensor or sensors to be faulty, remove the connector between the sensor and the vehicle’s wiring.
2. Using the proper socket, remove the faulty sensor.
3. Connect the new sensor to the vehicle’s wiring.
4. Install the new sensor.
5. Lower your car.
6. Start the engine.
7. Take a test drive.
8. Check to make sure the transmission shifts properly.
9. Check to make sure the cruise control works properly.
10. Wait to see if the check engine light goes off.
11. If everything is a-ok, you’re golden.

Congrats, you did it! Depositphotos

Tips From a Pro

Here are our top pro tips to help you diagnose and fix your transmission speed sensor.

• If your transmission becomes bucking-broncoesque, pull over. You’re likely to cause serious damage to a number of parts if you continue.
• A fluctuating speedometer may be a sign of a faulty transmission sensor.
• If you have a truck or SUV with enough ground clearance, you won’t need to jack up your car.

Life Hacks

Since you may not have access to the right tools, we also compiled a list of our best hacks to make your life easier and drain your pocket less.

• If you don’t have an OBD2 scanner handy, your local auto parts shop will loan you one.

How Often Do You Need To Test Your Transmission Speed Sensor?

Automakers build these sensors with a long lifecycle, the only reason you’d need to test or change the transmission speed sensor would be because it began to malfunction again.

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Got a question? Got a pro tip? Send us a note: [email protected] A vehicle speed sensor, or VSS, is a sensor that is used to determine how fast your vehicle is traveling. If your vehicle’s speedometer stops working or isn’t telling you the correct speed that you’re traveling, you likely have a faulty…

• How to Use a Digital Multimeter
• How to manually check the computer source with a multimeter

Part 1 of 3:

Disconnecting the VSS

1. Make sure the vehicle is turned off to avoid being shocked. Put the vehicle in park on level ground and turn off any lights or accessories that may draw power from the battery. Remove the key from the engine to make sure it’s completely turned off.^[1]
   1. Parking on level ground makes it easier for you to access the VSS.
2. Open the hood of the vehicle so you can access the engine. Locate and pull the release hatch near the driver’s side door to open the hood. Engage the interior release hatch on the front of your hood and raise the hood up. If your hood uses a rod to hold it open, move the rod to its slot.^[2]
   1. Make sure the hood is held securely in place before you lean into it to test the VSS.
3. Locate the VSS sensor near the transmission of your vehicle. Find the transmission dipstick and follow it to locate your transmission. The VSS will be a small sensor attached to your transmission by 2 wires and held in place by a bracket. It will also have a sliding pull tab on it. Look for a small, metal sensor surrounded by a metal bracket with a white and black wire connected to it.^[3]
   1. Vehicle speed sensors can be installed in different locations depending on what make and model of vehicle you have, but they measure the rotation of the transmission, so they’ll generally be located on or next to the transmission.
   2. Consult your owner’s manual to find the location of your VSS.

   Tip: If you don’t have your owner’s manual, or you’re unable to find your vehicle’s VSS, search the make and model of your vehicle online to locate the VSS.

4. Disengage the wiring harness connector from the VSS. There are 2 wires connected to the VSS, a black one and a white one. Both wires connect the VSS to your vehicle to ground the sensor and transmit information about you’re vehicle’s speed. Unplug the harness so you can take out the sensor.^[4]
   1. The wiring harness may be located on the underside of the VSS.
   2. If you can’t grip the harness with your fingers, use a pair of needle-nose pliers to disengage it.
5. Press the pull tab or button on the VSS to separate it. On the top or side of your VSS will be a sliding tab or a button. Engage the tab or button and gently pull on the sensor to release it from its housing.^[5]
   1. You may need to wiggle or slide the VSS out of its base.
   2. Don’t force or yank the VSS or you could damage it. Make sure you’ve engaged the sliding tab or the button that releases it.
   3. Some sensors may require you to remove 2 small screws to slide it out of place.
6. Unscrew the hold-down bolt and bracket to remove the VSS. Use a screwdriver to remove the bracket around the VSS. Then, use a socket wrench with a piece that fits over the bolt to twist the bolt and loosen it so you can pull out the sensor.^[6]
   1. Make sure you don’t lose the screws or bolts so you can replace the sensor.

Part 2 of 3:

Connecting the Multimeter

1. Plug the colored lead cables into their slots on the multimeter. Your multimeter will have a red and a black lead cable. Plug the black lead into the black colored terminal that’s labeled ‘COM’ which stands for common. Then, insert the red lead into the red colored terminal labeled ‘V’ for voltage, which is what you’re testing.^[7]
   1. Push the leads into their slots completely. They may ‘click’ into place when they’re fully connected.
2. Set the multimeter to AC to test your VSS. Look for a dial on your multimeter that has numbers and letters on it. The AC, or alternating current, setting may be labeled as AC, V with a squiggly line, or ACV. Turn the dial until the arrow or indicating line is pointing to the AC setting.^[8]
   1. Electrical devices, such as your VSS, use an AC current for power.
3. Plug a signal output and ground wire into the sensor. On the VSS is a slot where the sensor plugs into the vehicle. You can find a plug that fits into your VSS and contains a white signal output wire and black ground wire from auto supply stores. Make sure the plug fits your VSS securely.^[9]
   1. The plug uses a white signal output wire and a black ground wire to transmit signals from the device to your vehicle.
   2. You can also find plugs that contain the signal wire and ground online.
4. Connect the black lead and the red lead to wires on the plug. Take your black lead wire and clip it to the exposed wire at the end of the black ground wire plugged into the VSS. Then, take your red lead wire and connect it to the exposed end of the white signal wire plugged into the sensor.^[10]
   1. Make sure the red and black leads are securely connected.

   Tip: If the signal wire and ground wire are completely covered in sheathing, use a knife to strip about ¹⁄₄ inch (0.64 cm) of the wire sheathing to expose the wire beneath so you can clip your leads to it.

Part 3 of 3:

Rotating the Sensor

1. Find a drill bit that fits securely into the VSS. In order to simulate the movement of your vehicle to properly test the sensor, you need to rotate the gear inside of the VSS. Insert drill bits into the gear slot on the VSS until you find one that fits securely into it.^[11]
   1. Different sensors have differently sized slots, so try out a few bits until you find one that fits your VSS.
2. Connect the bit to your power drill. Loosen the chuck, or the piece on the end of the drill, by rotating it so the jaws open up. Slide the smooth end of the bit into the jaws and then slowly rotate the drill to tighten the jaws around the bit so it’s held securely.^[12]
   1. Give the bit a gentle tug to make sure it won’t fall out.
3. Spin the gears of the VSS by pulling the trigger on the drill. Hold the VSS in place with your hand and bring the drill up to speed slowly to rotate the gears in the slot the drill bit is inserted into. Allow the VSS to rotate at full speed so you can get an accurate reading.^[13]
   1. Start slowly and continue to increase the speed of the drill at a consistent pace so you don’t strip or damage the VSS.
4. Read the voltage on the multimeter to see if it increases with speed. While the VSS rotates, the multimeter will display a voltage reading. If the VSS is functioning correctly, the voltage on the multimeter will increase as the speed of the VSS rotation increases.^[14]
   1. If the voltage doesn’t increase or doesn’t display at all, then the VSS is damaged or faulty.

   Tip: Rotate the VSS at varying speeds to make sure the multimeter is accurately detecting speed changes.

5. Disconnect the plug and drill, and reinstall the VSS into your vehicle. Remove the drill bit from the VSS and take out the plug containing the white signal output and black ground wires. If the VSS is functioning properly, slide it back into its housing, reconnect the wiring harness, and replace the bracket and bolts.^[15]
   1. If your VSS isn’t functioning properly, replace it with the same make and model so it fits into your vehicle.
   2. Have a mechanic inspect your vehicle if your VSS is functioning but your speedometer still isn’t working properly.

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Speed sensors are usually located on the wheels of your car, and they perform the function of reading the overall number of wheel rotations and then delivers you the information. So how do you test the wheel speed sensors? Well, you can easily do this using a multimeter, and consequently, you will be able to tell whether there is any malfunction to make the needed repairs. Therefore, if you are looking to know how to use your multimeter to test a speed sensor, read through this article as you get to gain this valuable insight into the steps you need to follow. Subsequently, you will be in a better position to track the speed sensor’s speed, thereby get to drive meticulously.

Prep your car

When testing the speed sensors, you need to first prepare your vehicle by setting it on level ground and then switching off its engine. After that, make use of the transmission usually located in the park settings together with the emergency brake. Consequently, lift your car using a jack to remove its tires. Doing this enables you to test the sensors, thanks to your car’s ideal position. Some of the essential tools you need to test the speed sensor include;

• • Multimeter

• Floor jack
• Car manual
• Torque wrench
• Flying leads
• Tire iron
• Assistant
• Jack stands

Once you confirm you have all the essential equipment, you can then go right ahead and test the speed sensor, following the steps below in order.

Remove the connector

After placing your vehicle in a high position using a jack and the wheel is removed, you can now head to the wheel speed sensor. At this point, you should inspect and try to find the electrical connector located close to the wheel’s frame. Consequently, take off the sensor wire by unlocking its safety clasp and then pulling it away gently, and you will see the speed sensor terminals needed for testing.

Use your multimeter

Now that the speed senor terminals are exposed, you can then go ahead and use your multimeter. To do this, make use of the probes integrated into the design of your multimeter and attach them to the speed sensor terminals. Moreover, use alligator clips that typically go together with the multimeter to fasten the speed sensor firmly. As you attach the speed sensor terminals to do the test, ensure the probes never come into contact with each other because doing so causes the fluctuation of the readings. By doing this, you will generally have an easier time testing your speed sensor. Once you have confirmed that the terminals and probes are correctly connected, you then need to switch on the AC voltage. Consequently, you will instantly see the multimeter showing the readings up and down, with this a clear sign that you can now test the speed sensor.

Carry out the test with your multimeter

You now can go ahead and take the readings from your multimeter, and to do this, you need to spin the hub or wheel, with the reading varying depending on the wheel’s speed. The readings consequently display on the meter and fall to zero when the wheel stops spinning. If the multimeter is showing any readings while the wheel is spinning, this is a sign that the sensor is functional. Nevertheless, when no reading is being displayed regardless of whether the wheel is spinning or not, this is an indication the speed sensor has failed and needs to be replaced.

Replace the speed sensor

If the multimeter shows no readings, you should then go right ahead and get another speed sensor. Therefore, you should take off the damaged ones by going to the clips or nuts that are holding the speed sensor in place and loosen them gently. Eventually, the sensor will detach from your car, thereby allowing you to remove it. With the old sensors out, you then need to put in place the new and functional sensors. Nevertheless, you need first to inspect the area for any sign of rust, and after that, make use of sandpaper to scrub the surface that you intend to install the new sensor. After the new sensor is in place, use clips or crews to tighten it and then test using your multimeter whether any readings are being displayed when the wheel is spinning. You should also put back the rotors as well as brake pads if you had removed them to get a better view of the sensor. However, if the multimeter still does not show any readings, you then need to replace it. You should then return everything to its original place in an organized manner. Subsequently, after you are done with the sensor parts and brake pads, you should go ahead and restore the wheel on the hubs. Moreover, make sure everything fits perfectly and then make use of a ratchet and socket to tighten the lug nuts. You should then use the jack to gradually lower your car back to its original position by making use of the jack stand. Once you are done, use the lug nuts to fix the wheels to your vehicle and then use nuts to tighten them firmly with your hands. Consequently, make use of a torque wrench that is set to your vehicle’s torque capacity, and this value is usually found on the car’s user manual. Go ahead and put in place the nuts firmly and securely making use of the torque wrench, and this should take you about one or two minutes.

Conclusion

If you were looking to learn how to test a speed sensor with a multimeter, you now have an idea of what to do. Therefore, you never have to worry about not knowing the speed at which you are driving with this vital for improving your safety while on the road. However, once you are done testing the sensor using the multimeter, you always need to perform a test drive to confirm that everything is working as required. Once you are confident that everything is working fine, you can go ahead and use your car without any concerns about your safety on the road.
OPERATION The Vehicle Speed (VSS) Sensor input is used by the PCM to determine vehicle speed. The VSS generates a signal that increases in frequency proportionate to vehicle speed. The PCM has a base frequency stored in memory for a distance of one mile. By comparing the input and stored value, the PCM calculates vehicle speed. VSS types include: photo-optic, permanent magnet generators(The Vehicle Speed Sensor (VSS) is a magnetic pick-up that sends a signal to the Powertrain Control Module (PCM).) or hall effect technology. The PCM may use other sensors on the vehicle (ABS Wheel Speed) to validate VSS operation. VSS information is used to calculate vehicle loads including: torque converter application, cruise control, fuel cutoff/speed governance strategies, instrument panel speedometer and more. Modified drivetrain components such as final gear sets and/or tires can alter VSS input values to the PCM. Improper signals can alter Torque Converter Clutch (TCC) application, shift points, cruise control operation as well as many other systems relying on vehicle speed input. The sensor measures the rotation of the transmission and the PCM determines the corresponding vehicle speed. A faulty speed sensor due to loose connections, bad grounds, high resistance in the circuit, or opens in the circuit can cause the following symptoms

Vehicle Speed Sensor Symptoms

• Overheated transmission
• Increased emissions
• Poor fuel economy
• Stalling on deceleration
• Improper shift points
• Cruise control inoperative

Vehicle Speed Sensor Testing

1. Turn the ignition switch to the OFF position.
2. Disengage the wiring harness connector from the VSS.
3. Using a Digital Volt-Ohmmeter (DVOM), measure the resistance (ohmmeter function) between the sensor terminals. If the resistance is 190–250 ohms, the sensor is okay.

Vehicle Speed Sensor Replacement

REMOVAL & INSTALLATION
(older models) The VSS is located half-way down the right-hand side of the transmission assembly.

1. Apply the parking brake, block the rear wheels, then raise and safely support the front of the vehicle on jack stands.
2. From under the right-hand side of the vehicle, disengage the wiring harness connector from the VSS.
3. Loosen the VSS hold-down bolt, then pull the VSS out of the transmission housing. To remove the VSS, detach the wiring harness connector from it . . . then remove the hold-down bolt and bracket. . . and slide the sensor out of the transmission case
4. To install:
5. If a new sensor is being installed, transfer the driven gear retainer and gear to the new sensor.
6. Ensure that the O-ring is properly seated in the VSS housing.
7. For ease of assembly, engage the wiring harness connector to the VSS, then insert the VSS into the transmission assembly.
8. Install and tighten the VSS hold-down bolt to 62–88 inch lbs. (7–10 Nm).
9. Lower the vehicle and remove the wheel blocks.

REMOVAL & INSTALLATION (newer models)

1. Disconnect electrical plug
2. Remove mounting bolt

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