A vehicle’s speed sensor is a very sensitive component that interacts with the computer systems in a car to regulate the vehicle’s speed. The component also affects other areas, such as fuel consumption and how well a car idles.
A defective speed sensor will necessarily impact all the areas it interacts with and cause them to malfunction because of the failure to send the right signals.
This can be very risky for a car owner. The failure of most car sensors, like the speed sensor, usually alters the car’s safety.
So, ensure to understand the bad speed sensor symptoms that will be revealed in this article and how to fix the problems when they surface.
What Is a Speed Sensor?
A vehicle speed sensor (VSS) is a small device mounted on your car’s transmission that lets the car’s onboard computer know how fast you’re moving. It measures your car’s rotational speed and relays it to your car’s speedometer.
The vehicle speed sensor, also known as a transmission speed sensor or output shaft speed sensor, plays an active role in your car’s transmission and cruise control systems.
There are also ABS wheel speed sensors (WSS) on a vehicle’s wheel hubs (both on the front axle and rear axle). Their function is to monitor the rotation of each wheel and relay the data to the ABS control module for better vehicle control.
Speed Sensor Located
The location of a speed sensor is carefully designed to align with the specific layout and operational needs of each vehicle.
In most cases, the transmission speed sensor is mounted near the transmission’s output shaft, where it can accurately detect and record the shaft’s rotational speed.
For example, in Ford vehicles, the sensor is placed to capture output shaft speed with precision. The collected data is transmitted directly to the engine control unit (ECU) through a dedicated wiring system.
On the other hand, BMW models often include speed sensors on both the input and output shafts.
These sensors are strategically housed within the transmission pan, allowing them to collect detailed data from multiple points in the transmission system to improve accuracy.
In vehicles equipped with transfer cases, the speed sensor is typically located on the tail shaft at the rear of the transfer case.
This placement enables the sensor to monitor drivetrain performance, ensuring accurate readings during all-wheel-drive or four-wheel-drive operations.
What Is a Speed Sensor’s Working Mechanism In a Car?
The sensor gathers and sends data to the ECU about the vehicle’s speed. This information is used by the ECU to optimize how different parts of the car move.
The quantity of fuel and air used in combustion as well as transmission shifts are all included in this. Along with the precise time of injection, it also regulates the timing of the ignition. The gear changes are computed using the same data.
On occasion, one of the wheels will start to turn more quickly than the others. The sensor acts at this time by sending the information to the engine. The inputs help the ABS plan its course of action.
Axles, the transmission, and other parts are also subject to regulation. The speedometer also uses the inputs to display accurate speed and distance.
Two sensors make up the system, and they cooperate to transmit precise data. The terms input and output shaft sensors are used to describe them. One or both of these sensors will be involved in any speed sensor issues.
Bad Speed Sensor Symptoms
When a vehicle’s speed sensor is faulty, it begins to reveal some irregular symptoms that draw the car owner’s attention.
However, it will be difficult to fix the problems without understanding the message communicated by these symptoms. Some common symptoms revealed by a bad speed sensor include the following.
#1. Check Engine light display.
Several vehicle engine malfunctions can trigger the Check Engine Light, and one of the common malfunctions that can also trigger the display of the light is a faulty wheel speed sensor.
If you discover a consistent display of the Check Engine light, traction control light, and the ABS warning light on your car’s dashboard, ensure to find out what could be wrong. An OBDII Scanner can help assist in the diagnosis process.
#2. Cruise control failure to engage.
When a vehicle’s cruise control fails to receive any signal from the wheel speed sensor, the PCM will disable the cruise control system.
Therefore, if you discover that your car’s cruise control is failing to engage while you’re driving, it may be as a result of a bad wheel speed sensor.
#3. Irregular speedometer readings.
Most modern vehicles use the wheel speed sensor as a major input for the vehicle’s speedometer system’s operation. In that case, when the speed sensor goes bad, it automatically affects the proper functioning of the speedometer.
So, a vehicle’s speedometer will constantly display a false or random reading until the faulty wheel speed sensor is rectified. Ensure to fix this problem as soon as you notice it because it can be very risky.
#4. Transmission issues.
A vehicle’s transmission system relies on the signal from the wheel speed sensor to determine the timing for every gear shifting. When the wheel speed sensor fails to deliver the necessary signal, the transmission system will not be able to engage correctly.
The transmission is liable to exhibit signs like hard shifting, delayed shifting, and limited gear shifting operations due to a defective wheel speed sensor.
#5. The inability for transmission torque converter to apply the clutch.
Another sign that reveals that a vehicle speed sensor is bad is the transmission’s inability to apply the clutch. When this happens, there is no link established between the car’s engine and the transmission system.
This issue can also trigger transmission overheating, increased fuel consumption, and slippage. If you experience any of these challenges, it is most likely that your car’s wheel speed sensor is bad and needs to be fixed.
What Causes the Speed Sensor To Fail?
#1. An internal electrical fault in the speed sensor.
A speed sensor that is damaged internally can result in an abnormal output signal or no signal at all. Typically, the sensor can be tested with a digital voltmeter or oscilloscope.
Seek the help of a trusted mechanic if you suspect that you have a faulty VSS so it can be tested—and replaced if needed.
#2. Damage on the sensor itself.
It’s possible for the speed sensor to get damaged or cracked. Also, the plastic portion of the sensor can become brittle after prolonged exposure to the elements. The magnetic portion of the sensor may also become worn and damaged over time.
#3. Poor vehicle maintenance.
Failing to follow your vehicle maintenance schedule can increase the risk of speed sensor failure.
This device will not be able to produce correct readings if the magnetic pickup and/or toothed wheel become heavily covered in gunk, particularly old transmission fluid contaminants.
Expect a typical speed sensor to last from over 100,000 to almost 150,000 miles. To extend your speed sensor’s life, follow the recommendations of your owner’s manual in maintaining your vehicle’s transmission.
Diagnosing a Bad Vehicle Speed Sensor
If you think that your vehicle may have a bad speed sensor, proper diagnosis by a qualified mechanic (or yourself, if you have the ability) is important before parts start getting replaced.
While the symptoms mentioned above can point towards a failing sensor, a completely different issue may be causing those same symptoms.
Here are a few diagnostic methods to use to help identify the actual root cause:
#1. Visual Inspection.
Step one is to have a thorough look at the speed sensor(s). A mechanic will check for any visible damage to the sensor, such as cracks, corrosion, or loose connections.
They’ll also look at the wiring harness for any signs of wear, fraying, or even rodent damage (yes, it does happen).
#2. OBD2 Scanner.
Almost all vehicles on the road today are equipped with on-board diagnostic (OBD) systems that can detect and store trouble codes related to various components, including speed sensors.
A scan tool can be used to retrieve any stored codes and determine if they are related to a speed sensor issue. Some common speed sensor-related codes include:
- P0500 (Vehicle Speed Sensor Malfunction)
- P0501 (Vehicle Speed Sensor Range/Performance)
- P0715 (Input/Turbine Speed Sensor Circuit Malfunction)
- P0720 (Output Speed Sensor Circuit Malfunction)
#3. Multimeter Testing.
In some cases, a mechanic may use a multimeter to test the resistance and continuity of a speed sensor and its wiring. This method is particularly useful for identifying issues with passive sensors, such as variable reluctance sensors.
The measured values can then be compared to the manufacturer’s specifications to determine if the sensor is functioning as it should.
#4. Oscilloscope Testing.
An oscilloscope is a powerful diagnostic tool that allows a mechanic to visualize the waveform generated by a speed sensor. By connecting the oscilloscope to the sensor’s wiring, they can assess the quality and consistency of the signal.
A faulty speed sensor may produce an erratic, weak, or absent signal, indicating the need for replacement.
#5. Road Testing.
Finally, the automotive tech can perform a road test to assess the vehicle’s behavior and confirm the diagnosis.
During the road test, they will monitor the speedometer, odometer, transmission shifting, and other systems affected by the speed sensor. This is often done with a professional scan tool that reads and records live data.
How To Fix Bad Speed Sensor?
#1. Understand the Function and Symptoms of a Faulty Speed Sensor.
Before beginning the repair process, it’s crucial to understand what the speed sensor does and recognize the symptoms of its malfunction.
A vehicle speed sensor (VSS) typically measures the rotation of a wheel or the transmission shaft and relays this data to the car’s computer to regulate things like speedometer readings, gear shifting, cruise control, and ABS functionality.
When it begins to fail, common symptoms include an erratic or non-functioning speedometer, rough or delayed gear shifts, check engine light illumination, or malfunctioning cruise control.
Understanding these symptoms ensures you’re diagnosing the correct component and not overlooking related issues.
#2. Locate the Speed Sensor According to Vehicle Specifications.
Speed sensors are generally located on the transmission or near the wheel hubs, depending on whether it’s a vehicle speed sensor or a wheel speed sensor for the ABS system. Consult your car’s service manual or a trusted repair guide to find the exact location.
This information will not only help in gaining access for repairs but also in understanding whether you’re dealing with a sensor that’s accessible from underneath the vehicle or from the engine bay. Accurate location also prevents wasting time removing unnecessary parts.
#3. Disconnect the Battery and Prepare Safety Measures.
Safety is a priority whenever working with a car’s electrical system. Disconnect the negative terminal of the battery before attempting any repair to avoid shorts or electrical injuries.
Park the vehicle on a flat surface, engage the parking brake, and, if needed, use wheel chocks. If the sensor is located underneath the vehicle, raise the car using a hydraulic jack and secure it with jack stands.
These precautions protect you from electrical accidents and physical injury while working underneath the car.
#4. Inspect the Sensor Wiring and Connectors for Damage.
Often, issues with a speed sensor aren’t caused by the sensor itself but by corroded, damaged, or loose wiring. Carefully inspect the wire harness connected to the sensor, checking for frayed insulation, bent pins, or signs of moisture ingress.
Clean dirty connectors with electrical contact cleaner and secure any loose plugs. Sometimes, a fix is as simple as reattaching a connector that came loose due to vibrations. Be thorough in this inspection to avoid replacing a good sensor unnecessarily.
#5. Use a Diagnostic Scanner to Confirm Fault Codes.
Modern vehicles store fault codes when a sensor malfunctions. Use an OBD-II scanner to read the error codes stored in your car’s computer. Codes such as P0500 (Vehicle Speed Sensor Malfunction) can confirm that the VSS is indeed the issue.
This helps you rule out problems like faulty transmission solenoids or wiring faults. A scanner also allows you to clear codes after the fix to monitor whether the issue is truly resolved, adding confidence to your repair.
#6. Remove Obstructions to Gain Access to the Sensor.
In some vehicles, other engine components, such as the air filter housing, battery, or underbody shields, might obstruct access to the speed sensor. Remove these components carefully using appropriate tools, keeping track of bolts and clamps.
Photographing the layout beforehand can help during reassembly. By creating ample working space, you reduce the risk of damaging nearby components and make the repair process less frustrating and more efficient.
#7. Remove the Faulty Speed Sensor with Care.
Once you have access, disconnect the electrical connector from the speed sensor. Most sensors are secured with one or two bolts—typically 10mm or Torx fasteners. Use a ratchet with the appropriate socket or bit to remove these bolts.
Gently twist and pull the sensor out of its housing. If it’s stuck due to grime or corrosion, apply a little penetrating oil and let it sit before trying again. Avoid forcing it out with tools that could damage the sensor mounting point or surrounding transmission housing.
#8. Clean the Mounting Area Before Reinstalling or Replacing.
With the sensor removed, inspect the sensor port or mounting hole. Use a lint-free cloth to remove any debris or corrosion that may affect the new sensor’s fit or performance. A clean, flush connection ensures the new sensor can relay accurate data.
You can also apply a small amount of dielectric grease to the sensor’s electrical connector to protect it from moisture and ensure a good electrical connection during reassembly.
#9. Replace or Reinstall the Speed Sensor and Test.
If the sensor is beyond repair or testing shows it’s faulty, replace it with an OEM or high-quality aftermarket equivalent. Insert the new sensor into the mounting hole and secure it with the bolts removed earlier.
Reconnect the wiring harness, making sure the clip snaps into place firmly. Once everything is reassembled and any removed components are returned to their original positions, reconnect the battery and start the engine.
Monitor for warning lights and take the vehicle for a short test drive to ensure proper speedometer function and smooth gear transitions.
#10. Reset the ECU and Monitor for Recurring Issues.
After replacing the sensor, it’s advisable to reset the vehicle’s ECU by using a diagnostic scanner to clear any remaining error codes. If you don’t have access to one, disconnecting the battery for a few minutes may force the ECU to reset on some vehicles.
During the test drive, monitor the speedometer and transmission behavior closely. If issues persist, further diagnostics may be necessary, such as checking the reflector ring or transmission control module. Consistent performance and absence of warning lights indicate a successful fix.
Right Time to Replace Your Vehicle Speed Sensor
The lifespan of a vehicle speed sensor typically ranges between 30,000 and 50,000 miles, but its durability can vary depending on driving conditions, maintenance habits, and external factors. To ensure proper vehicle performance, consider the following details:
Factors Affecting Lifespan
The longevity of a speed sensor can be reduced by several factors. Improper installation, such as misaligned fittings or loose connections, can cause premature failure.
Similarly, electrical disturbances, like short circuits or voltage spikes, may damage the sensor’s components. Additionally, exposure to harsh environments—including water, dirt, and extreme temperatures—can wear down the sensor more quickly than usual.
Regular Diagnostics and Inspections
Including the speed sensor in your regular vehicle maintenance routine is dangerous. Periodic inspections can identify early signs of sensor failure, such as erratic speedometer readings, transmission issues, or illuminated warning lights on the dashboard.
Detecting these symptoms early can prevent further complications and ensure timely repairs or replacements.
Replacement Timing
While there is no fixed schedule for replacing a speed sensor, replacing it proactively when symptoms arise—rather than waiting for complete failure—helps maintain optimal vehicle performance.
For vehicles frequently exposed to challenging conditions, replacing the sensor closer to the lower end of its lifespan range may be advisable.
Importance of Timely Replacement
A failing speed sensor can affect dangerous systems like the speedometer, transmission, ABS, and traction control.
Replacing a worn or defective sensor as soon as it shows signs of malfunction not only ensures accurate data for the vehicle’s electronic systems but also enhances your safety and overall vehicle reliability.
Is It Safe to Drive with a Failing Speed Sensor?
While it’s technically possible to operate your vehicle without a properly functioning vehicle speed sensor, it is strongly discouraged.
A faulty VSS can negatively impact multiple aspects of vehicle operation—which is why it’s best to replace a bad speed sensor as soon as possible.
If you observe any of the symptoms mentioned above, take your vehicle to a mechanic immediately—or address the problem (if you’re handy with cars) yourself.
This ensures your continued safety on the road and helps prevent costly engine and transmission damage down the line.
Failing to replace a faulty sensor can affect both of these systems as they won’t have the necessary information that they need to perform optimally.
Not only will these repairs cost you hundreds to thousands of dollars, but they can also be harder to fix and put your vehicle out of commission for a longer than it has to be.
Remember that what can resolve Jeep Cherokee speed sensor problems, such as resetting the ABS light, can be different from solutions for other vehicle models like a Chevy, so make sure to check your vehicle carefully.
How much does it cost to replace the wheel speed sensor?
The estimated cost of replacing a bad wheel speed sensor varies from $125 to $265. While the labor cost of fixing the part is around $69 to $87, as the case may be. However, the cost of the component varies from one location or auto part dealer to another.
The total cost of replacement will also be a function of the vehicle make and model, as some may be expensive compared to others.
So, ensure to find out how much it cost to get a wheel speed sensor replacement for your vehicle make and model within your neighborhood.
FAQs.
Q: Can you drive with a bad speed sensor?
Driving without a speed sensor or with a bad speed sensor can be a big risk. The speed sensor’s role is very essential to the safety of a driver. The sensor helps determine the vehicle’s speed to know when necessary to apply the brakes.
So, driving with a faulty speed sensor will not allow the computer to determine the necessary speed level to increase the engine power or apply the brakes. This may lead to a fatal accident because the safety system is defective.
If you are wondering, “How long can you drive a car without speed sensor?” This shouldn’t be something to consider. Immediate replacement is advisable if you find out that your car’s speed sensor is bad.
Q: Does a bad wheel speed sensor make noise?
A bad wheel speed sensor can affect several areas of a vehicle and reveal its symptoms in different ways.
Besides symptoms like the display of the ABS warning light, traction control problems, etc., a bad speed sensor may also result in a noise coming from the vehicle’s wheel.
Once any of the symptoms that reveal a bad wheel speed sensor is noted, ensure to rectify the problem as soon as possible. It is better to solve a problem at the initial stage than to solve it when it is more complicated.
Q: Can a bad wheel speed sensor cause brake problems?
Of course, a bad wheel speed sensor can result in brake issues. However, the problem does not usually span across to the regular brake system in the vehicle. The problem often affects the anti-lock brakes.
A defective wheel speed sensor will affect a car’s anti-lock brakes and make it malfunction. Once this occurs, the ABS warning light will be triggered immediately to display on the car’s dashboard.
Q: Can a bad wheel speed sensor cause limp mode?
Yes, a defective wheel speed sensor can cause limp mode in a car. A bad wheel speed sensor can result in a loss of traction control and stability. This, in turn, can trigger the ABS system to disable the traction control and stability systems.
This consistent malfunctioning can result in limp mode. Limp mode is triggered when a car’s computerized systems automatically detect a crucial engine or transmission fault, thereby hibernating some of the important components in the vehicle.
So, when a car’s wheel speed sensor goes bad, it can move the car into limp mode because it is a critical sensor among the components of the vehicle.
Q: Can a bad wheel speed sensor cause rough idle?
A faulty speed sensor will send wrong signals to a vehicle’s computerized systems, which affects the function of other areas of the car.
So, for those asking, “Can a bad speed sensor cause rough idle?” A bad speed sensor will cause rough idle and make a vehicle burn excess fuel than expected.
The wrong signals sent from the speed sensor area to the vehicle’s fuel system can also cause other engine issues like reduced acceleration and so on.
Therefore, if you discover that your vehicle’s wheel speed sensor is faulty, ensure to replace it immediately because the after-effect can be ugly.
Q: Can a bad wheel speed sensor cause reduced engine power?
Yes, the wheel speed sensor is a very sensitive sensor, and its malfunction can cause reduced engine power.
The sensor is also designed to enhance transmission shifting while the engine is running. Meanwhile, when the sensor becomes faulty, it will fail to communicate with the vehicle’s computer system to regulate the engine’s revving.
When this happens, the vehicle will not only go into limp mode; it will release the reduced engine power light because the systems are linked together.
If you are also asking, “Can a bad speed sensor cause stalling?” This may not be a direct effect; however, the impact of a faulty speed sensor can further lead to stalling because it affects the engine.
Final Words
A bad wheel speed sensor is not just a challenge because a component needs to be changed; it is a challenge because its impact is felt by several other parts of the engine compartment.
Bad speed sensor symptoms are easy to identify if you follow the areas pointed out in this article. If you ever experience these symptoms unveiled above, ensure to act immediately to rectify the issue as soon as possible.
If there is a need to replace the bad speed sensor, ensure to do so. Failure to replace the part may lead to further damages that can be beyond easy control.