2004 Cadillac CTS - Transmission Speed Sensor

Bad Transmission Speed Sensor Symptoms

The transmission speed sensor, also known as a vehicle speed sensor or (VSS), calculates the gear ratio of the transmission and the speed at which the engine and transmission are turning to determine the vehicle's speed. There are usually two transmission speed sensors, which include the input shaft speed (ISS) sensor, and the output shaft speed (OSS) sensor. These sensors work together to send data to the vehicle's computer so the transmission engages the appropriate gear for the best operation in the current driving conditions. Transmission speed sensors may not last forever, and can wear out or become weak over time. This can lead to inaccurate readings being sent to the computer, and as the sensor condition worsens, transmission performance may suffer. In the case that the actual gear ratio does not match the desired gear ratio, you may see a Check Engine light or a service transmission light. If one or both sensors wear out or fail electronically, you may notice harsh or improper gear shifting, high RPMs before changing gears, or your cruise control may stop working. If you've experienced these problems, or if your Check Engine or other warning lights are active, it's important to complete your diagnosis before beginning your repair. At O'Reilly Auto Parts, we carry replacement transmission speed sensors, including ISS and OSS sensor connectors for most vehicles. Your local store can also read your Check Engine light codes for free to help you begin your diagnosis, and help you find the best parts to complete your repair.