Subaru LEGACY 2002 Quick Reference Index page 402

VEHICLE DYNAMICS CONTROL (VDC) SYSTEM
VDC
C: FUNCTIONS USED IN VEHICLE'S BEHAVIOR STABILIZATION CONTROL
VDC function
TCS function
ABS function
NOTE:
! "Braking control" is effected by the VDCCM as follows:
The VDCCM calculates the required braking force for each wheel and sends signals to the VDC
hydraulic unit. The hydraulic unit's motor pump is then operated to generate the required hydraulic
pressure. Further, it controls the hydraulic unit's solenoid valves to increase, maintain or decrease
the hydraulic pressure applied to the brake wheel cylinder as required.
When the brakes are applied by the driver, however, the braking force is controlled by the hydraulic
pressure resulting from the driver's action.
! "Engine output control" is effected by the VDCCM as follows:
The VDCCM calculates the target engine output for each condition, and compares it with the cur-
rent engine output. Based on the result of comparison, it determines the number of cylinders for
which fuel injection is to be stopped and sends a command to the engine control module. The tar-
geted engine output is then achieved.
! "AWD control" is effected by the VDCCM as follows:
When necessary, the VDCCM sends a command to the automatic transmission control module.
According to the command, the transmission control module controls the transfer clutch so that
the torque is distributed between the front and rear axles optimally.
The VDC control module (VDCCM) determines the driver's intention from the data provided by the
steering angle sensor, braking pressure sensor, engine-related sensors and other relevant sources and
recognizes the result as the target vehicle behavior. At the same time, it determines the vehicle's actual
behavior from the data provided by the yaw-rate sensor, lateral G sensor, ABS sensor and other rele-
vant sources. Then, the module compares the target and actual vehicle behaviors to estimate how the
vehicle is running (whether it understeers, oversteers, slips or is in other condition), and based on the
result, performs braking control of individual wheels, engine output control and AWD control as neces-
sary to correct the vehicle's running condition.
The TCS constantly receives signals from the relevant sensors to monitor the vehicle speed. When the
running wheels slip exceeding a certain limit, it performs braking control of individual wheels, engine
output control and AWD control as required to maintain optimal traction and adequate side force.
The ABS constantly receives signals from the relevant sensors to monitor the vehicle speed. When the
slip of wheels during braking exceeds a certain limit, it performs braking control of individual wheels
and AWD control as required to maintain optimal traction and adequate side force.
VDC-4