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The Transmission Sensor is an essential component of your car’s automatic transmission system. It monitors input and output shaft speeds to provide this data to the PCM for processing.
Without speed data, the PCM cannot accurately regulate shifting gears within the transmission. This could cause shifts to shift more frequently or abruptly than usual and even damage internal components like valve bodies and hydraulic lines.
Input Shaft Speed Sensor
Transmission sensors are essential components in your vehicle, providing signals that influence speedometer readings, antilock brakes, ignition timing and cruise control functions. A malfunctioning speed sensor could result in sending error codes directly to the PCM; and should it cause your vehicle to shift gears improperly then this could trigger the check engine light on your dashboard.
Your transmission’s input shaft speed sensor is an electrically controlled sensor which sends a voltage signal directly to the transmission electronic control unit (TECU), depending on its rotational speed when entering its main case. Once received by TECU, this signal is compared with those from main shaft and output shaft sensors to calculate an overall transmission gear ratio.
Step one in determining whether your transmission requires replacement is to inspect its input shaft speed sensor, with the TECU providing warning when it suspects one to be defective. Additionally, they will display any electrical shorts detected between power or ground in your speed sensor’s circuit and that could indicate problems within.
Modern cars typically contain multiple speed sensors that monitor the speeds of both their input shafts and output shafts, commonly referred to as input shaft speed (ISS) sensors and output shaft speed (OSS) sensors, to provide accurate transmission data to their powertrain control module.
ISS sensors may be located either on the input shaft of your transmission, or mounted to an auxiliary upper countershaft gear in its rear case. Some transmissions utilize both types of ISS sensors; such as some 4L80E automatics and most 2004 and later 4R70W or 4R75 transmissions.
Input shaft speed sensors (ISS sensors) are utilized in many vehicles to monitor clutch slip and allow the PCM to make necessary adjustments based on actual input shaft speeds. If one becomes misalign or experiences electrical issues, this can severely impair performance and compromise transmission performance.
Output Shaft Speed Sensor
Output Shaft Speed Sensors are small devices usually located on the output shaft of a transmission. Their main task is to measure how fast your vehicle is traveling, then send this information directly to its control module for processing.
Transmission speed sensors are an integral component of your transmission control unit (TCU) that help determine the appropriate gear ratios for efficient driving. Furthermore, these sensors communicate with anti lock brakes, power steering, ignition timing systems and other devices to keep them all operating as intended.
As soon as your output shaft speed sensor fails, it could result in difficulty shifting and could even trigger the Check Engine light. Knowing the signs and symptoms of a failing sensor is important so you can address any potential repairs promptly to save yourself a costly repair bill down the line.
Automatic transmissions typically feature two transmission speed sensors: an input shaft speed sensor (ISS) and output shaft speed sensor (OSS). The ISS monitors input shaft speed while the OSS monitors output shaft speed.
The TCU uses these signals to calculate and display the actual gear ratios of the transmission when in use, then relays that information back to the powertrain control unit, or ECU, of a vehicle.
Modern vehicles feature various kinds of speed sensors. They range from basic wheel speed sensors that monitor how fast each wheel turns to complex crankshaft position sensors that measure where and in what direction camshafts are turning.
Some transmissions also offer a third speed sensor known as the output shaft speed sensor. This small device connects directly to the output shaft of a transmission and includes magnetic pickup, coil, and gear toothed rotor components.
The TCU uses square wave signals produced by gear teeth rotating inside of a rotor to assess transmission gear ratios and creates shift control signals to adjust hydraulic pressure for changing gears accordingly.
Position Sensor
Position sensors use physical information about objects or assemblies to convert this into electrical output signals that can either be digital or analog in nature, used typically within computer control systems for system or operations management purposes.
Sensors can be designed to detect an object or assembly based on its distance, rotational motion or any combination thereof. In order to provide reliable signals it is critical that their position be accurately established.
Potentiometers and rotary encoders are among the most frequently used position sensors. A popular type of potentiometer used in automotive applications is known as a potentiometric potentiometer.
These devices have excellent sensitivity, resolution, and accuracy; are non-contact and provide great linearity; are affordable; widely available; can be used in industrial applications, semiconductor technology, disk drives and linear displacement measurements (from millimeters to nanometers).
Inductive position sensors use alternating currents to measure linear movements, without making contact with anything, thus offering non-contacting measurements with increased durability than their contacting counterparts. They’re used widely in motor control and other demanding applications.
Magnetic position sensors use ferromagnetic materials to detect magnetic fields. They’re heavy-duty and non-contact sensors, suitable for various environments and can even be made out of different materials.
Magnetorestrictive position sensors rely on the magnetorestriction property of ferromagnetic materials such as iron, nickel and cobalt when exposed to magnetic fields. When exposed, these materials expand, producing strain signals in a waveguide running along their travel axis and producing strain signals along its travel axis.
Signal conversion converts this physical signal into an electrical one for transmission to a computer for use in determining position or speed determination of objects, making these sensors suitable for industrial and medical uses (including MRI scanners ).
Position sensors can also be used to track the location of vehicles on roads. Traffic signals rely on them to ensure cars remain within the flow of traffic. They can also detect when an emergency vehicle approaches an intersection and are also useful in many other applications that require accurate and reliable detection of objects or assemblies.
Temperature Sensor
Temperature sensors come in various forms and forms are designed for specific uses; from those most often employed in industrial settings to everyday life applications. Each has been developed specifically.
A thermistor is a popular temperature sensor used in numerous applications such as medical devices and gas analysis. These sensitive devices detect small temperature variations quickly and display them accurately, making them useful in many different situations.
These sensors come in an assortment of sizes and designs; some surface-mount while others utilize probe technology.
Most of these devices feature high degrees of accuracy and sensitivity, are easy to use, affordable, and come in an assortment of materials.
Resistance temperature detectors (RTDs), another popular form of temperature sensors, feature a coil of conductors whose resistance changes with increasing or decreasing temperatures. These devices tend to be extremely accurate and may use high-purity conductors like platinum.
Temperature sensors provide a cost-effective and versatile way to measure temperature, and are frequently employed in applications as varied as controlling refrigerators, regulating water temperatures, and in battery chargers to avoid overcharging.
Other types of temperature sensors include thermocouples and semiconductor-based temperature sensors, which use dual integrated circuits with two diodes that measure temperature by providing voltage signals that detect it and store the readings to be converted into output signals later.
Thermocouples are an extremely reliable and accurate temperature sensor, boasting an operating temperature range of -200 degC to 1750 degC. They have become one of the most commonly used sensors.
These sensors provide a simple solution for measuring transmission fluid temperature in vehicles. As negative temperature coefficient thermistors, their internal resistance varies in response to transmission fluid temperature.
These sensors can often be installed into difficult to access locations that would make standard surface-mounted sensors inapplicable; making them a fantastic alternative to RTD and thermocouple sensors in many different industries, including sensitive industrial areas.