Vehicle Speed Sensor: Description and Operation

VEHICLE SPEED SENSOR (VSS)
Detects speed going out. Outputs frequency signal to PCM. PCM controls operation as follows:
1. Fuel injection
2. Ignition timing
3. Shift/torque converter clutch scheduling
4. EPC

Operation
Uses a variable reluctance sensor. Sensor generates a sine wave type waveform with a frequency.
- High frequency as vehicle velocity increases.
- Low frequency as vehicle velocity decreases.

NOTE:
- Installed in transmission (4x2) or transfer case (4x4).
- If EPC solenoid is shorted to ground, PCM outputs DTC for VSS. Diagnose EPC solenoid first, then check VSS.