Speedometer with odometer and trip meter: Speedometer
The main instrument unit has an electronic speedometer. The ABS control module receives speed information from the rear left wheel speed sensor. The information is processed and sent continuously to the main instrument unit control module pin 3.
The information is sent as a square wave pulse and varies periodically between B+ and 0V. The main instrument unit supplies the power and the ABS control module grounds the output. This takes place 29 times per wheel revolution.
With the wheels stationary, the voltage may be either B+ or 0 V.
The main instrument unit uses the frequency to calculate the vehicle speed.
The speedometer is controlled by a stepping motor that is pulsed from the main instrument unit control module, which converts the frequency modulated signal to km/h or mph. A correction is made depending on the tire size that has been programmed, whereby the speed information is sent to the bus.