Vehicle Speed Input

Vehicle Sensor Buffer And TCCM Schematic:

OPERATION
The vehicle speed sensor buffer informs the Transfer Case Control Module (TCCM) about the speed of the vehicle in miles per hour. Such information is essential to inform the TCCM to prohibit range shifts at speeds above 3 mph. The vehicle speed sensor (VSS) is a variable-reluctance magnetic sensing device that converts tone wheel rotation into a frequency and voltage output proportional to the vehicle speed. The frequency and voltage signal is sent to the vehicle speed sensor buffer which converts the speed sensor output into a useful pulse signal. The vehicle speed sensor buffer then, pulses circuit 1567 to ground at a rate of 4000 pulses per mile. Whenever the vehicle speed sensor buffer grounds circuit 1567, the voltage at TCCM connector pin D8 returns to 5 volts. The TCCM reads the 4000 pulses-per-mile (1.11 Hz per mph) signal to determine vehicle speed.