Vehicle Speed Sensor: Description and Operation

Vehicle Speed Sensor Operation:

PURPOSE
The vehicle speed sensor reports road speed to the ECM. This information is used to synchronize emission systems and to adjust for various engine demands.

LOCATION
Mounted to the transmission tailshaft.

CONSTRUCTION
The vehicle speed sensor outputs a 4-pulse signal for every revolution of the rotor shaft, which is rotated by the transmission output shaft via the driven gear. After this signal is converted into a more precise rectangular waveform by the waveform shaping, circuit inside the combination meter, it is then transmitted to ECM. The ECM determines the vehicle speed based on the frequency of these pulse signals.