No Vehicle Speed Sensor Signal

NAME OF CODE
No Vehicle Speed Sensor Signal

WHEN MONITORED
With engine temperature greater than 104° F, Manifold Absolute Pressure (MAP) approximately 350 torr, (or MAP vacuum 15 to 16"), and engine speed between 1400 and 3000 RPM.

SET CONDITION
No signal from the vehicle speed sensor for more than 15 seconds on two (2) consecutive trips.

THEORY OF OPERATION
The vehicle speed sensor is a hall-effect type sensor used to detect the vehicle speed. The Powertrain Control Module (PCM) calculates the vehicle speed based on the Vehicle Speed Sensor (VSS) signal. The PCM supplies 5 volts to power up the sensor. Sensor ground is supplied by the PCM. The PCM also supplies a 5-volt pull-up voltage to the sensor. The VSS signal is created with the sensor alternates the 5-volt pull-up from high to low.

POSSIBLE CAUSES
- VSS adapter misaligned or not seated properly
- Open or shorted signal circuit
- Speedometer pinion damaged
- Open 5-volt supply circuit
- Open sensor ground circuit
- Failed vehicle speed sensor
- Failed PCM