Difference Between Vehicle Speed Sensor And Transmission Speed Sensor? 

Difference Between Vehicle Speed Sensor And Transmission Speed Sensor? When you examine fuel-injected engines on modern cars, you will notice that many sensors work together to inform the engine or transmission computer what is happening. The vehicle computer needs to understand if the wheels are turning well if the engine is spinning and ensure all component remains within specifications.

However, a speed sensor is regarded as one of the various types of engine sensors. Note that some vehicles have wheel speed sensors, while others have engine and transmission speed sensors.

But you need to understand the difference between vehicle speed and transmission speed sensors. So to understand their differences, I will have to explain what they are individual. How To Reset Electronic Throttle Control Manually Chrysler 300

What Is A Vehicle Speed Sensor?

The vehicle speed sensor (VSS) is a small component mounted on your vehicle’s transmission, allowing the vehicle’s onboard computer to understand how fast the car is moving.

So How Does The Speed Sensor Work?

It works by measuring the rotational speed of all gears in the transmission system. The vehicle speed sensor helps convert the rotational speed measurement of all gears into an analog signal. It sends it to the electronic control units (ECUs) inside your vehicle. 

When this happens, the vehicle’s ECUs will then use the signal to adjust the vehicle’s speedometer readings, the transmission system, and the ABS module.

The vehicle’s cruise control system might also rely on the information generated by the speed sensor. When there’s no information generated, your vehicle won’t be able to maintain a constant vehicle speed.

So What Is A Transmission Speed Sensor?

A vehicle transmission speed sensor communicates directly to the ECU or TCU, which helps an automatic transmission understands what gear it should be in. However, there are two main types of transmission speed sensors: the first is the input shaft speed sensor, and the other is the output shaft speed sensor.

The Input Shaft Speed Sensor

The input shaft speed sensor measures the torque converter and speed of the input shaft, which matches the engine’s speed.

The Output Shaft Speed Sensor

The vehicle’s output shaft speed sensor helps monitor the speed at the back of the transmission, which happens after the transmission’s gear ratio is already applied. Note that the odometer or speedometer can determine a vehicle’s ground speed.

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How Can You Tell If The Transmission Sensor Is Bad?

Note that a transmission speed sensor helps calculate the transmission gear ratio when in use. As you may know, every vehicle has two-speed sensors: The Output Shaft Speed Sensor and the Input Shaft Speed Sensor, which work together to send the transmission data to the vehicle’s ECU. So how can you tell if the transmission sensor is bad? Below are some signs showing you if your transmission speed sensor is bad.

  • Failure of the cruise control 

One of the duties of the speed sensors is to monitor the input and output shaft speed. However, this isn’t the only function of these sensors. Their duties also include checking the cruise control. The cruise control is a system that automatically controls the car’s speed. 

The proper functioning of the cruise control depends on the data sent from the transmission speed sensors. Once the cruise control fails to work, it simply means the sensors have malfunctioned. This also means that the PCM will transmit an error code to the ECU, which will shut down. When this happens, you’ll be required to consult your mechanic immediately to have your vehicle inspected.

  • Improper or harsh shifting

You will have issues shifting gears whenever no speed signals are coming from any of the sensors. This is because the powertrain control module (PCM) won’t be able to control them correctly. When this happens, it will make the transmission not work efficiently. 

What will happen is either it shifts more quickly or roughly than expected. Another issue caused by failed sensors happens in gear shift timing, which will cause the interval between shifts to be extended. Whenever gear shifting becomes hard, the transmission’s internal components can become damaged.

  • The check engine light indicates

As we all know, the check engine light is a vital component in a car. Whenever it illuminates, it means there’s a problem with the car. However, you won’t be able to tell if or not it comes from the transmission speed sensors except if you check. Note that if you can’t carry out this by yourself, contact a mechanic to examine the cause of the problem. Remember that sometimes the sensors may need to be replaced completely, and a qualified mechanic can only do this.

What Happens When The Transmission Speed Sensor Goes Bad?

Whenever there’s a loss of speed signals from all sensors, there will be a problem shifting gears. This is due to the inability of the powertrain control module (PCM) to control them efficiently. When this happens, it will make the transmission not work well. 

However, it will either shift more quickly or roughly than expected. But another problem caused by bad sensors is gear shift timing, which will cause the interval between shifts to be extended. Also, the transmission’s internal components can become damaged whenever gear shifting becomes hard.

How Many Speed Sensors Does A Transmission Have?

In most modern cars, you will notice two transmission speed sensors, which can be found at the input shaft and another at the output shaft. The transmission speed sensors happen to be very important to its powertrain operation.

Its input/output sensors help calculate the transmission’s actual gear ratio while in use. So usually, two sensors communicate the transmission data to a car’s powertrain control module. 

The input sensor, which is the first sensor, monitors the speed of the transmission’s input shaft. At the same time, the output sensor is the second, which monitors the output shaft speed. 

Whenever those sensors aren’t working well, the cruise control may not work well, the vehicle’s transmission may shift roughly or sluggishly, or the speedometer may malfunction.

Can A Bad Wheel Speed Sensor Cause Transmission Problems?

Indeed, the transmission systems are essential components in a car. Whenever it starts to malfunction, it simply means there is a serious issue that needs to be handled carefully. However, all parts of a car are interconnected. But when one begins to malfunction, others may follow suit, leading to a complete vehicle breakdown.

First, you need to understand the various sensors mounted in your transmission that control various functions. There are different sensors, such as the brake light switch, wheel speed sensor, throttle position sensor, transmission speed sensor, or coolant temperature sensor. All these help to ensure that your transmission is perfectly working at its optimal level.

How Long Can You Drive A Car With A Bad Speed Sensor?

First, you need to know the duty of speed sensors. This would give you a clearer view of how long you can drive whenever all of the speed sensors go bad

Usually, a bad speed sensor will not make your car not run. This means you might still be able to drive your car for long. But on modern cars, there are tech-integrated systems that allow faulty speed wheel sensors to bring a vehicle to a halt.


I have shown you that a vehicle speed sensor is essential to ensure the cruise control, speedometer, and transmission work well.

When you drive with a bad speed sensor, you won’t be able to know how fast you’re going, and this could compromise your safety. Not only that, you’ll likely experience poor driving conditions due to harsh and irregular transmission shifting.

So to prevent this from happening to you, make sure to contact a mechanic to inspect your wheel speed sensor and replace it if necessary.

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