Skylark V6-3100 3.1L VIN M SFI (1996)
Speedometer Head: Description and Operation
With Electronic Cluster
DESCRIPTION
The Vehicle Speed Sensor (VSS) generates a signal that indicates the vehicle speed. The signal is processed by the powertrain control module (PCM)
to supply inputs to the speedometer and odometer.
OPERATION
The VSS is mounted in the transaxle and generates an AC voltage signal with a frequency proportional to vehicle speed. The PCM takes the voltage
pulses from the sensor and uses them to close a solid state output switch. The output terminal is switched to ground at a rate proportional to vehicle
speed. The speedometer and odometer are switched at the same frequency that the sensor generates at. The speedometer and odometer are operated by
a circuit board in the instrument cluster that converts pulses received from the PCM into a control signal for the vacuum fluorescent display.
Check for a broken, or partially broken, wire inside the insulation which could cause system malfunction but prove "GOOD" in a continuity/voltage
check with a system disconnected. These circuits may be intermittent or resistive when loaded, and if possible, should be checked by monitoring for a
voltage drop with the system operational.
