Vehicle Speed Sensor

Vehicle Speed Sensor (VSS) is an electronic relay that is mounted on transmission. As transmission turns, VSS provides speedometer with a vehicle speed input (voltage pulses). This input is used to drive speedometer. Speedometer then converts vehicle speed input into a more precise waveform and provides Powertrain Control Module (PCM) and cruise control module with its own vehicle speed input. Cruise control module converts this input into a vehicle speed. For vehicle speed sensor replacement procedures, see appropriate ELECTRONIC CONTROLS article in AUTOMATIC TRANSMISSIONS. RES/ACC switch can also be used to tap-up vehicle speed. In order to do this, cruise control system must be engaged and operating. Tapping-up is performed by quickly moving cruise control switch up into RES/ACC position and releasing it (or tapping switch into RES/ACC position). Do not hold cruise control switch in RES/ACC position, or cruise control system will enter accelerate mode. Tap-up is a function in which cruise speed can be increased by one MPH increments (one tap = one MPH increase).