Speed Sensor Symptoms, Causes, and Solutions: What Are They?

Speed sensor symptoms might be showing you that your vehicle’s health is in decline. No matter the problem or your level of expertise, we are here to help you understand and fix the issue.

What is The Causes of Bad Speed Sensor Let’s get into it.

What Are Some Symptoms of a Bad Speed Sensor?

Some symptoms of a bad speed sensor include faulty cruise control, malfunction of the speedometer, and rough gear changes. Other common symptoms of this problem are improper shifting, the car slowing down when idle, and the stability control light coming on.


Car Slows Down When Idle

A malfunctioning speed sensor can also affect the vehicle’s idle speed control. To maintain a stable idle speed when the vehicle is at a standstill, the idle speed control system relies on input from various sensors, including the speed sensor.

Odometer While Car Idle

If the sensor sends incorrect signals, the engine control unit will receive inaccurate data about the vehicle’s speed. This will cause the car to slow down or stall unexpectedly when idle. It often leads to inconvenience and potential safety hazards, especially in heavy traffic or at intersections.

Cruise Control Does Not Work

Transmission speed sensors serve a dual purpose of overseeing the rotational speeds of both the input and output shafts. The cruise control (or autopilot) also manages other control functionalities. When these sensors don’t transmit precise data to the car’s onboard computer, the powertrain control module (PCM) displays error codes to the vehicle’s electronic control unit (ECU).

On receiving the error code, the ECU then disables and deactivates the cruise control for safety. Once you notice that using the autopilot doesn’t work after pressing the button, it is advisable to seek the expertise of a mechanic. The mechanic can inspect the vehicle thoroughly to find out the root cause of the autopilot malfunction.

Harsh or Improper Shifting

Modern automatic transmissions depend heavily on the data provided by their sensors. This data helps the transmission to use the best gear accurately based on current driving situations. A faulty vehicle speed sensor often supplies inaccurate data, which leads to jarring or improper gear shifts.

Driver Struggling To Shift Gear

Symptoms of this inaccurate data include sudden gear transitions, delayed shifts, or the transmission becoming locked in a specific gear. Overall, these issues undermine the quality of the driving experience and can worsen transmission issues.

Speedometer Malfunction

When a car’s speedometer suddenly stops functioning, it means that the speed sensor has encountered a problem. A bad sensor means that the speedometer will be unable to display your vehicle’s current speed.

Speedometer Showing Zero

Not knowing your traveling car speed is a serious problem, especially when there is minimal traffic to give you a rough estimate of your speed. This situation can lead to issues with law enforcement or even cause sudden and preventable accidents.

Rough Gear Changes

In addition to affecting automatic transmissions, a bad vehicle speed sensor can affect vehicles with manual transmissions. Generally, the engine control unit (ECU) uses data from the crankshaft position sensor to determine the optimal timing for gear changes in manual transmissions.

If the sensor is not working as it should, the ECU may struggle to align the engine speed sensor with gear changes, resulting in rough shifts or difficulty engaging gears. This symptom can lead to a less enjoyable driving experience and potentially damage the transmission speed sensor over time.

Stability Control (SC) Light On

Thanks to stability control systems installed in modern vehicles, drivers can easily control and stabilize their cars during slippery and rough conditions. These control systems are designed to use information from other sensors, like the speed sensor, to manage each wheel’s speeds and braking forces while driving.

Vehicle Stability Control Light On Odometer

If the car’s speed sensors fail, the SC and check engine light is activated on the dashboard. When this happens, the system has been compromised, ultimately affecting the car’s traction control and handling. The risk is losing steering control during bad weather or traveling on bad roads.

The dangers of a faulty stability control system are higher in adverse weather conditions. Other noteworthy malfunction symptoms include ABS sensor light activation, check engine light activation and torque converter clutch issues.

What Are the Causes of Speed Sensor Malfunction?

The causes of speed sensor malfunction range from low voltage, electrical issues, and bad wiring and connections, but you shouldn’t overlook the impact of poor maintenance. Humidity seeping into the components is another culprit that tends to fly under the radar but causes speed sensor failure.

Equally destructive are dirty connectors, which cause an unwanted break in transmission. Lastly, good old wear and tear cannot be ignored as well because no part lasts forever!

Low Voltage

A stable electrical supply is important for your speed sensor to function properly, as you can imagine. Hence, you should make sure your battery is in tip-top performance. If your battery’s underperforms, you can expect all sorts of malfunctions. Some of them include failing to give you accurate signals or a total shutdown.

The sensor is not the only component affected by Low Voltage. Other electrical components within the vehicle are also at risk. To arrest this, ensure you maintain and check your alternator, battery, and electrical connections regularly.

Electrical Fault

Faulty electrical components are culprits for many vehicular issues, and sensors are not left out. Faulty connectors, damaged wiring, and short circuits are common electrical issues that disrupt the flow of electrical signals to and from the wheel speed sensor. With time, these electrical issues result in inaccurate and inconsistent readings, causing damage to systems that rely on the sensor.

Regularly check and repair wiring components and connectors to curb these faults if found damaged or slightly corroded from weather indices.

Wear and Tear of Speed Sensors

Sensors, like all mechanical parts, undergo wear and tear with usage. Over time, exposure to road debris, moisture, temperature fluctuations, and vibrations can affect the sensor’s delicate components. As these components degrade, the sensor’s accuracy and reliability diminish, potentially leading to erratic or incorrect readings.

Teared Apart Sensor Wire

While wear and tear are inevitable, adhering to regular maintenance schedules and replacing worn-out sensors can extend the sensor’s lifespan and prevent unexpected failures.

Poor Maintenance

Neglecting routine maintenance can cause sensor problems. Dirty or contaminated sensor surfaces can hinder the sensor’s ability to detect wheel speed sensor rotation accurately.

When dirt, grease, or debris pile up, they can mess with the sensors and cause them to send incorrect signals. That’s why it’s crucial to stick to simple maintenance tasks like changing transmission fluid and brake pads. Plus, don’t forget to clean the sensor and the space around it regularly while doing routine maintenance to keep it working at its best.

Bad Wiring or Connections

Your sensor must be safely and firmly connected to your car’s electronic system before it can transfer data in an accurate manner. If it is wired poorly, you can expect the flow of data to be disrupted. This often leads to partial or total failure of the sensor.

Wire System Of Car_s Engine

Vibrations, collisions, or time can contribute to damaged wiring or poor connections. Periodic inspections of the sensor’s connections and the surrounding wiring can help identify and rectify these issues before they escalate into full-blown failures.

How To Fix a Faulty Speed Sensor

To fix a faulty speed sensor, you should first find and remove it. After removing the sensor, employ a multimeter to test its resistance levels, comparing the obtained readings with the manufacturer’s specifications. If these readings significantly differ, you need a prompt speed sensor replacement.

Take Out the Speed Sensor

You should be able to locate the sensor itself before you begin trying to fix a defective speed sensor. The sensor’s precise location can vary depending on the vehicle’s make and model. However, it is mainly found on the transmission housing or wheel hubs.

Park your car on a level surface, use the parking brake, and ensure the ignition is off. Depending on the sensor’s location, you should raise the car using a jack and secure it on jack stands for safety. This is particularly important if the sensor is on the vehicle’s underside.

Carefully disconnect the wiring connector attached to the sensor. This is often a simple clip or plug mechanism. Most sensors are secured using screws or bolts. Use the appropriate tools to remove these fasteners carefully and gently pull the sensor out.

Once it’s out, check the sensor closely. You want to examine it for any signs that it is wearing, damaged, or contaminated. Try cleaning the sensor with a mild solvent. This ensures it is free from the usual debris.

Test It Using a Multimeter

As long as you have the sensor out, it’s time to test it with a multimeter. If you don’t already know, multimeters measure voltage, current, and resistance across two given points. Hence, it’s an invaluable tool for this part of the process.

Set your multimeter to the “Ohms” (Ω) orResistance” mode. Make sure the vehicle’s ignition is off. If your sensor has visible signs of damage or corrosion, consider testing the wiring harness before proceeding.

Insert one probe of the multimeter into the wiring harness connector’s positive terminal and the other probe into the negative terminal. A functioning harness should display a reading close to zero resistance. If the resistance is too high or infinite, there might be an issue with the wiring.

Carefully touch the multimeter’s probes to the two terminals of the sensor. The multimeter should display a resistance reading. Consult your vehicle’s manual for the specific resistance range your sensor should fall within. If the reading is significantly out of range, the sensor is likely bad and needs replacement.

Some multimeters have a continuity setting. To do this, spin the gear on the sensor (or simulate wheel rotation), then check if the multimeter still shows a connection as the gear moves. If the connection breaks, it might mean there’s a problem with the sensor’s magnetic part or its inside wires.

Cross-reference your multimeter readings with the specifications provided in your vehicle’s manual or by the manufacturer. If the readings are significantly different, it is a strong indication that the sensor is indeed faulty and requires replacement.


What Is the Main Difference Between Input and Output Speed Sensors?

The main difference between input and output speed sensors is that input sensors monitor engine input shaft rotation while output sensors track transmission output shaft speed. Input sensors aid gear selection and are vital for smooth and efficient gear shifts, while an output speed sensor works to influence shift timing.

How Much Does It Cost To Replace a Speed Sensor?

It costs about $100 to replace a speed sensor in most instances. Generally, the replacement cost depends on your car’s make and model. It is advisable to get quotes from reputable mechanics or repair shops for a more accurate estimate tailored to your situation.


After reading this guide, concerns over these symptoms should no longer trouble you. Here are our final thoughts on the key points covered in this article:

  • Once you can pick out the speed sensor symptoms, you’re done with half the job.
  • You should check out symptoms like rough gear changes and inaccurate speedometer readings and repair them immediately.
  • All these are key reasons to keep your car in good shape, especially as often as your mechanic recommends it.
  • Fixing a malfunctioning sensor is not a simple process, especially for new drivers. It involves strategic steps such as locating the sensor, carefully removing it, and testing it with a multimeter.

With the right tools and info, you’re ready to fix that problematic sensor. Good luck.

Rate this post
Ran When Parked