Wheel-speed signal output

Fig 1: Identifying Wheel-Speed Signal Output

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Several other systems in the vehicle need to know the wheel speed. The ESP control module is connected to the P-bus and transmits information about the speed of each wheel.

This information is processed in the main instrument unit into vehicle speed in km/h (mph). The speed is corrected to the tire size that has been programmed. This vehicle speed is then sent out over the I-bus.

The engine management system is connected to the P-bus and therefore has access to the same speed information.

Fig 2: Identifying Engine Management System

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Fig 3: Engine Management System Circuit Diagram (1 Of 2)

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Speed information can be sent even when the ABS, foot brake, ESP OFF or central warning lamps are on. The information is sent as long as one of the rear wheel sensors is working and the control module is working and supplied with power.

For more information on wheel speed on the bus, see BUS AND DIAGNOSTICS COMMUNICATION and MAIN INSTRUMENT UNIT .

Fig 4: Engine Management System Circuit Diagram (2 Of 2)

Courtesy of SAAB-SCANIA OF AMERICA, INC.