9-5 Sport Wagon (9600) L4-2.3L Turbo (B235) (2003)
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Information Bus: Description and Operation
Bus Operation - General
Description of Operation, Function Chains
Description Of Operation, Function Chains
A large number of function chains can be identified in the bus system. Below are three examples of important ones.
1. Vehicle speed
Cars with ABS
Vehicle speed is sensed by the ABS through an inductive sensor at each wheel. The sensor supplies the control module with alternating current, the
amplitude and frequency of which increase with increasing wheel speed. The frequency is proportional to wheel speed, 29 Hz at a speed of one wheel
revolution per second. The ABS control module uses the 4 wheel speeds to prevent wheel lock-up on braking.
Several other systems in the car need to know vehicle speed. Cars with the ABS control module, which is not connected to the bus, have a control
module output for each wheel speed. A transistor grounds each output 29 times per wheel revolution.
The main instrument panel is connected with a lead to the output for the LH rear wheel speed signal. The rear wheel is used to provide the most
accurate measurement of distance from a nondriving wheel. In the main instrument panel, the frequency-modulated signal is converted to km/h. The
main instrument panel makes a correction depending on programmed tyre type.
Cars with TC/ABS or ESP
On cars with Traction Control or ESP, the TC/ABS or ESP control module is connected to the P-bus. The TC/ABS or ESP control module sends out
wheel speed for all four wheels, but the other systems only use information on the speed of the LH rear and RH front wheels.
Wheel speed RL: The TC/ABS or ESP control module transmits the bus message "wheel speed rear left xxx km/h". This message is used by MIU
(internal). MIU sends "Vehicle speed" further along the P-bus and I-bus.
Wheel speed FR: The TC/ABS or EPS control module transmits the bus message "wheel speed front left xxx km/h" This message is used by Trionic.
Since the main instrument panel is connected to a bus, all control modules connected to the bus are supplied with information on the speed of the
left-hand rear wheel and the odometer reading.
The table of transmitted bus messages shows that MIU transmits the vehicle speed and that it is used by: Trionic, SID, ACC, Audio and TWICE. MIU
also transmits the odometer reading, which is used by SID for the service indicator.
The various systems use the vehicle speed for the following functions:
