4R70W

4R70W Transmission


Vehicle Speed (VSS) Sensor

The source of vehicle speed (VSS) is model dependent. Possible sources of vehicle speed input are anti-lock brake sensor (ABS), a gear-driven vehicle speed sensor (VSS), or an output shaft speed sensor (OSS). The VSS signal is either an A/C signal whose frequency changes with speed, or an SCP data message depending on the source. Some applications will have both. The vehicle speed signal is an input to various vehicle subsystems such as the powertrain control module (PCM), instrument cluster (speedometer and odometer), speed control system, etc. The vehicle speed source must be operational to enter output state control (OSC) mode for diagnostics.

Regardless of the type of vehicle speed system, the PCM always uses the OSS for transmission and engine control.