Vehicle Speed Sensor (VSS)

VSS generates a predetermined number of pulses per sensor revolution (4 pulses per revolution on some models, or 8 pulses per revolution on other models). VSS input is used by PCM to determine vehicle speed and distance traveled, and to maintain set speed during cruise control operation.

PCM interprets speed sensor input along with TP sensor closed throttle input. This enables PCM to determine if a closed throttle deceleration or normal throttle idle (vehicle stopped) condition exists. During deceleration, PCM controls IAC motor to maintain a desired MAP value. During idle (vehicle stopped), PCM controls IAC motor to maintain a desired idle speed.