Vehicle Speed Sensor (VSS)

VSS is located on transmission extension housing (2WD models) or on transfer case extension housing (4WD models). PCM uses VSS to determine vehicle speed and distance traveled.

VSS is an 8-pole switch which provides a pulse or switching rate, proportional to vehicle speed, to the PCM. By comparing the number of pulses to time elapsed, the PCM determines vehicle speed and distance traveled. VSS generates 8 pulses per sensor revolution. This signal, along with a closed throttle signal from the TP sensor, indicates a closed throttle deceleration to the PCM.

Under deceleration conditions, PCM adjusts the Idle Air Control (IAC) motor to maintain desired MAP value. During idle (vehicle stopped), the PCM receives no signal from the VSS. The PCM adjusts the IAC motor to maintain a desired engine speed.