Circuit Operation

The vehicle speed sensor generates a signal which indicates the vehicle speed to the electronic control module (ECM), the A/C cut control unit (automatic transaxle) and the cruise control unit (XS).

The vehicle speed sensor no. 2 is mounted on the back of the speedometer. The speedometer cable rotates a magnet which closes the contacts of a reed switch as it rotates. The reed switch contacts close and open four times for each revolution of the speedometer cable.

Each time the reed switch closes, the vehicle speed inputs are grounded by the reed switch. When the reed switch is open, the electronic control module (ECM) input, the cruise control unit (XS), and the A/C cut control unit (automatic transaxle) are held at 12 volts by voltage through a pull-up resistor in the component.

When the vehicle is moving, the units receive a series of voltage pulses. The rate at which the pulses are received indicates the vehicle speed.