Econoline E550 V8-7.3L DSL Turbo VIN F (2002)
Transmission Speed Sensor: Description and Operation
4R70W
Output Shaft Speed (OSS) Sensor
The output shaft speed (OSS) sensor is a magnetic pickup, located at the output shaft ring gear, that sends a signal to the powertrain control module
(PCM) to indicate transmission output shaft speed. The OSS sensor is used for torque converter clutch (TCC) control, shift scheduling and to determine
electronic pressure control (EPC).
Vehicle Speed (VSS) Sensor - Model Dependent
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.
