May 21, 2024

What does the output shaft speed sensor do?

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When discussing the workings of a cars transmission system speed sensors play a crucial role in providing accurate information, for optimal performance. Specifically the output shaft speed sensor is a component that helps monitor the speed of the transmissions output shaft. By identifying and transmitting this data to the vehicles control unit the output shaft speed sensor facilitates gear changes, smooth driving and overall efficient operation of the transmission. In this article we will examine the details of the output shaft speed sensor exploring its purpose, functionality and typical signs of malfunction.

Understanding Speed Sensors

Before we explore the details of the output shaft speed sensor it’s important to grasp the concept of speed sensors, within a vehicles transmission system. Speed sensors as defined by the Society of Automotive Engineers (SAE) are instruments that gauge the number of revolutions or distance covered per unit of time. These sensors offer information to the vehicles control modules, which then utilize this data to manage output components and ensure optimal functionality.

In a transmission system speed sensors generally fall into two categories; input shaft speed (ISS) sensor and output shaft speed (OSS) sensor. While the ISS sensor keeps track of the input shafts speeds the OSS sensor detects how fast the transmissions output shaft is spinning. Together these sensors work in harmony to provide transmission data to the vehicles powertrain control module (PCM).

The Role of the Output Shaft Speed Sensor

The turbine speed sensor, also known as the output shaft speed sensor is, in charge of keeping track of how the transmissions output shaft’s spinning. Positioned near the back of the transmission this sensor detects how quickly the output shaft is rotating, which directly correlates to how the vehicles wheelsre moving.

The information gathered by this sensor is essential for aspects of the vehicles performance. Primarily it helps the PCM determine the gear ratio for smooth driving. By comparing the desired gear ratio with the one adjustments can be made to ensure gear shifts and optimal power distribution. Moreover this speed sensor plays a role in controlling systems, like cruise control and traction control both of which depend on speed data.

How Does the Output Shaft Speed Sensor Work?

To understand how the output shaft speed sensor works it’s essential to grasp the technology behind these sensors. Modern vehicles typically use two types of speed sensors; sensors and digital sensors.

Inductive sensors, also called sensors, consist of a magnet surrounded by a wire coil. As the output shaft rotates, teeth or magnets, on the shaft pass by the sensor creating an analog AC waveform. This waveform is then converted into a signal by the sensor. Sent to the PCM for processing.

Digital sensors produce a wave signal. They rely on steel teeth passing by the sensor or small magnets embedded in the bearing seal to generate pulses. The sensor interprets these pulses. Converts them into a signal transmitted to the PCM.

Regardless of which type of sensor is used the output shaft speed sensor continuously monitors the transmissions output shaft speed. This data is vital for the PCM to determine factors such, as vehicle speed, gear shifting patterns and other control functions.

Signs of a Failing Output Shaft Speed Sensor

Like any part, in a car the speed sensor, on the output shaft can wear out with time. If this sensor starts acting up or stops working altogether it can cause problems that impact how well your vehicle performs and drives. Here are a few typical signs to watch out for that suggests your output shaft speed sensor might be failing;

1. Erratic or Inaccurate Speedometer Readings

A common indicator of an output shaft speed sensor is when the speedometer shows incorrect readings. This sensor is essential, for ensuring that the vehicles instrument panel displays speed information. When this sensor malfunctions the speedometer can exhibit behavior, such, as displaying speeds or fluctuating unexpectedly during driving. In instances the speedometer may completely cease to function.

2. Delayed or Harsh Shifting

The output shaft speed sensor is essential for the transmission to shift gears smoothly. It gives information to the cars computer helping it choose the gear for seamless shifting. If this sensor malfunctions it can cause delays or rough transitions, between gears. This may result in gear changes or missed shifts making driving feel rough and unpleasant.

3. Malfunctioning Cruise Control

One more sign that the output shaft speed sensor is failing is when the cruise control system of a vehicle acts up. Cruise control needs speed details to keep a pace while on the road. When the output shaft speed sensor isn’t working properly the PCM might not get speed data causing the cruise control system to struggle in keeping a speed. Sometimes the cruise control might not even activate all.

4. Illuminated Check Engine Light

If the output shaft speed sensor isn’t working properly it could cause the cars diagnostic system to record an error code and turn on the check engine light on the dashboard. This signals that there might be an issue, with either the sensor itself or the entire transmission system. It’s crucial to get the vehicle checked and fixed promptly to avoid any harm.


The output shaft speed sensor is a part of a cars transmission system. It plays a role in providing accurate speed information to the PCM. By keeping track of how fast the transmissions output shaft’s spinning this sensor helps ensure gear changes, optimal power distribution and proper operation of features like cruise control. It’s important to be able to recognize signs that the speed sensor may be failing, such as readings on the speedometer or delays in shifting gears. If you notice any of these issues it’s best to get in touch with a mechanic or technician away, for diagnosis and repair.

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