No Vehicle Speed Sensor Signal

NAME OF CODE:
No Vehicle Speed Sensor Signal

WHEN MONITORED:
With engine running more than 31 seconds, engine temperature greater than 180°F, transmission not in park or neutral, brakes not applied, engine RPM greater than 1800, and MAP vacuum less than 11".

SET CONDITION:
No signal from the vehicle speed sensor (VSS) for more than 11 seconds.

THEORY OF OPERATION:
The vehicle speed sensor is a hall-effect type sensor used to detect the transmission output shaft speed. The Powertrain Control Module (PCM) calculates the vehicle speed based on the VSS signal. The PCM supplies 8 volts from cavity 44 to power up the sensor. Sensor ground is supplied by PCM cavity 51. The PCM also supplies a 5.0 volt pull up voltage to the sensor from cavity 5. The VSS signal is created when the sensor alternates the 5.0 volt pull up from high to low.

POSSIBLE CAUSES:
- Open or shorted signal circuit
- Speedometer pinion damaged
- Open 8-volt supply circuit
- Open sensor ground circuit
- Failed vehicle speed sensor
- Failed PCM