Last Updated on October 24, 2023 by Kevin Chen
Image source carparts.com
Are you sure you are driving at the right speed? What if you get pulled over for driving beyond the designated speed limit yet you assumed that you were cruising at the right speed? Well, the speed sensor could be the main culprit to your agony. A fault speed sensor is likely to lead to the inaccurate readings on your vehicle’s speedometer.
So, how can I say that I have a bad speed sensor and are there ways to correct a bad speed sensor? Read on as we discuss everything about a bad speed sensor.
What is the function of a speed sensor in a vehicle?
Also known as Vehicle Speed Sensor (VSS), wheel speed sensor or transmission speed sensor, this is a critical electronic component that forms part of a vehicle’s transmission system. Its main function is to determine the speed at which the vehicle is cruising by measuring the rotation of the wheel, the sprocket and the axle. It will then relay this information to the vehicle’s ECU or computer.
The information from the speed sensor will then be used to control various aspects of a vehicle which include:
- Speedometer: The VSS will send its data to the speedometer which will then display the real-time speed of the vehicle on the dashboard.
- Cruise control: The actions of the vehicle’s cruise control system will solely depend on the data it gets from the speed sensor. The information from the sensor will allow the sensor to maintain constant speed or adjust the throttle when necessary.
- Anti-lock Brake System (ABS): A vehicle’s ABS system also depends on the data relayed by the speed sensor. Once the ABS knows the vehicle’s speed, it will execute necessary adjustments on the braking force preventing the wheels from locking up.
- Transmission system: The transmission system will also react based on the data from the speed sensor. The system will determine the appropriate gear to engage at what speed of the vehicle.
Where is the speed sensor located in a vehicle?
Before you even know your speed, sensor is bad, it will be smart to know its exact location in the vehicle.
The location of a speed sensor will always vary depending on the type and model of the vehicle. In most vehicles, it is located on the directly on the transmission system or on the differential component of the vehicle.
In some cases, it can be a single sensor that monitors the cruising speed of all the wheels or it can be multiple sensors that monitor the speed of each wheel. This means that you first have to determine the number of speed sensors on your vehicle.
The surest way of determining the location of the speed sensor is by consulting the manufacturer’s manual. You can also check on the internet whereby different forums will have adequate information about this.
If you are not sure about locating the sensor, consider seeking help from a professional automotive technician. They will be able to find it and even find out the problems that it is having (if any).
Symptoms of a bad speed sensor
Image of speedometer
At this point, we can proceed to discuss the most common symptoms of bad speed sensors.
Constant transmission problems
Since the VSS is directly connected to a vehicle’s transmission system, you are likely to experience problems on the transmission when the sensor becomes faulty. As we have discussed, the transmission system receives data from the sensor. What if the data being relayed is inaccurate, or no data is relayed at all? There will be some problems with the behavior of the transmission system.
For example, the transmission system will shift the gear erratically rather than smoothly. Sometimes it may stay at a single gear for long when it is supposed to do a linear shifting. Poor acceleration is another problematic sign caused by a bad speed sensor. Are you experiencing poor fuel efficiency? The transmission system could be getting wrong data from the speed sensor.
Malfunctioning speedometer
This is the most direct sign of the transmission sensor problems since the problem will be displayed right at your face. You will be able to tell this when the speedometer is not displaying correct figures on the dashboard.
As an experienced driver, you can easily approximate the speed at which your vehicle is cruising. From the experience, you will be able to tell if the figures displayed on the dashboard are out of order.
However, the problem may be beyond the bad speed sensor if the dashboard does not move at all.
Malfunctioning cruise control
The working mechanism of a cruise control system depends on the data from the speed sensor. The system will be able to maintain a constant speed and adjust the throttle accordingly if it gets accurate data from the cruise control system.
A bad speed sensor won’t be able to relay relevant information as needed by the cruise system which will subsequently malfunction.
ABS warning light
Many other problems in a car’s brake system can trigger the ABS warning light. Bad speed sensor is just one of them. Since the ABS also depends on the information from the transmission speed sensor, it will be difficult for it to function smoothly if it keeps getting wrong data.
However, if the speed sensor is in good condition and the ABS light is still on, proceed to inspect other issues on your car’s brake system.
Check engine lights and trouble passing
A ‘Check engine’ light can be caused by other numerous problems. One of them being a faulty speed sensor. Once you have cleared al other problems that could have possibly triggered the light, try to check on the speed sensor.
Another problem symptom is hard passing. This happens when you struggle to overtake other vehicles. Your car’s transmission system is not getting adequate power required to overtake.
If you experience these symptoms and any other transmission-related problem, consider checking out your speed sensor. But still it is important to have your car diagnosed so that the specific problem can be identified and rectified.
How to test transmission speed sensor
Knowing the symptoms of a bad speed sensor is not enough. You need to narrow down and find their appropriate solutions. It all starts with testing and diagnosing the speed sensor. Here are the steps to follow when testing a vehicle’s transmission speed sensor.
- Go through the vehicle’s manual: It all starts with familiarizing yourself with the vehicle. Read the manual to find out details about the car. The manual should tell you the exact location of the speed sensors and how many they are in your vehicle.
- Locate the speed sensor: From the previous step, you can tell the exact location of your vehicle’s speed sensor. Probably it is somewhere on the drivetrain which is on the rear axle. Once you locate it, identify the electronic connections used and the wiring.
- Visual inspection: Visually inspect the sensor and its wiring system. Watch out for any sign of physical and electrical damage on the sensor. These signs could include corrosion, rust, and even the worn-out edges of the wire. Consider doing a repair or a replacement if you notice any physical defect on the wires.
- Carry out resistance test: Time to get deep into the electronics aspect of testing a speed sensor and we will start with the resistance test. You will do this to ensure that the resistance of the sensor and its components is withing the manufacturer’s recommendations. You will use your multimeter to perform this test. Again, you will use the manufacturer’s manual for reference.
- Perform a voltage test: Using the same multimeter, test the output voltage of the sensor as it spins. Take note that the voltage should increase gradually as the speed of the sensor increases
- Test the signal of the speed sensor: You will need an oscilloscope to do this test. Simply check the output signal coming out of the speed sensor. The good thing about an oscilloscope is it will give you visual image of the signal’s behavior and you will be able to tell if the output has any issues.
- Clean the speed sensor: Dirt, dust and debris are the most common culprits for a bad speed sensor. Even after implementing the previous steps, ensure that you clean the components of the sensor before calling it a day. Sometimes there could be no electrical fault, just an issue with the cleanliness.
If you are not conversant with the maters pertaining electronics and mechanics, consider hiring a professional mechanic to do the speed senor diagnosis. They will save you the headache at some fees.
Replace the speed sensor
What if you follow all the steps above but still nothing seems to bear fruits? You should consider replacing the whole speed sensor. Buying a new transmission speed sensor will save you all the troubles and will also deliver the expected results. You only need to ensure that the new sensor is compatible with the model of your vehicle.
I hope that this guide has given you all the tips you should know about speed sensors. For any detailed information, consider finding a professional.
If you want to find more Electronic Components Distributors, please check out the following articles:
Electronic Components Distributors In the USA
Electronic Components Distributors In UK
Electronic Components Distributors In China
Electronic Components Distributors In India
Electronic Components Distributors In Singapore
Electronic Components Distributors In Malaysia
Electronic Components Distributors In Vietnam
Electronic Components Distributors In South Korea
- Where to buy IC chips? The Best Guide? - March 26, 2024
- Breaking Down Barriers: Overcoming Obstacles in Cross-Border Electronic Component Trade - March 4, 2024
- Everything You Need to Know About Amplifier IC Chips - March 4, 2024