Antilock Brakes / Traction Control Systems: Description and Operation
System Diagram
VDC Function
^ In addition to the TCS/ABS function, the driver steering amount and brake operation amount are detected from the steering angle sensor and pressure sensor, and the vehicle's driving status (amount of understeering / oversteering) is determined from information from the yaw rate sensor/side G sensor, wheel sensor, etc., and this information is used to improve vehicle stability by controlling the braking and engine power to all four wheels.
^ The SLIP indicator lamp flashes to inform the driver of VDC operation.
^ During VDC operation, the body and brake pedal lightly vibrate and mechanical noises may be heard. This is normal.
^ The ABS warning lamp, VDC OFF indicator lamp, and SLIP indicator lamp might turn on when the vehicle is subject to strong shaking or large vibration, such as when the vehicle is on a turn table or a ship while the engine is running. In this case, restart the engine on a normal road, and if the ABS warning lamp, VDC OFF indicator lamp, and SLIP indicator lamp turn off, there is no problem.
TCS Function
^ The wheel spin of the drive wheels is detected by the VDC/TCS/ABS control unit from the wheel speed signals from the four wheels, so if wheel spin occurs, the rear wheel right and left brake fluid pressure control and engine fuel cut are conducted while the throttle value is restricted to reduce the engine torque and decrease the amount of wheel spin. In addition, the degree the throttle is opened is controlled to achieve the optimum engine torque.
^ Depending on road circumstances, the driver may have a sluggish feel. This is normal, because the optimum traction has the highest priority under TCS operation.
^ TCS may be activated any time the vehicle suddenly accelerates, suddenly downshifts, or is driven on a road with a varying surface friction coefficient.
^ During TCS operation, it informs a driver of system operation by flashing SLIP indicator lamp.
ABS Function
^ The Anti-Lock Brake System is a function that detects wheel revolution while braking, and it improves handling stability during sudden braking by electrically preventing 4 wheel lock. Maneuverability is also improved for avoiding obstacles.
^ If the electrical system breaks down, then the Fail-Safe function starts, the ABS becomes inoperative, and the ABS warning lamp turns on.
^ Electrical System Diagnosis by CONSULT-II is available.
EBD Function
^ Electronic Brake Distributor is a function that detects subtle slippages between the front and rear wheels during braking, and it improves handling stability by electronically controlling the Brake Fluid Pressure, which results in reduced rear wheel slippage.
Fail-Safe Function
VDC / TCS SYSTEM
In case of Throttle Control System trouble, the VDC OFF indicator lamp and SLIP indicator lamp are turned on, and the condition of the vehicle is the same as the condition of vehicles without VDC / TCS equipment. In case of trouble to the Throttle Control System, the ABS control continues to operate normally without VDC / TCS control.
CAUTION: If the Fail-Safe function is activated, then perform the Self Diagnosis for VDC/TCS/ABS control system.
ABS, EBD SYSTEM
In case of electrical problems with the ABS, the ABS warning lamp, VDC OFF indicator lamp and SLIP indicator lamp will turn on. Simultaneously, the VDC/ TCS/ABS become one of the following conditions of the Fail-Safe function.
1. For ABS trouble, only the EBD is activated and the condition of the vehicle is the same condition of vehicles without TCS/ABS equipment.
2. For EBD trouble, the EBD and ABS become inoperative, and the condition of the vehicle is the same as the condition of vehicles without TCS/ABS, EBD equipment.
NOTE: In condition 1 described above, an ABS Self Diagnosis sound may be heard. That is a normal condition because a self diagnosis for "Key Switch ON" and "the First Starting" are being performed.
Hydraulic Circuit Diagram
CAN COMMUNICATION
System Description
Controller Area Network (CAN) is a serial communication line for real time application. It is an on-vehicle multiplex communication line with high data communication speed and excellent error detection ability. Many electronic control units are equipped onto a vehicle, and each control unit shares information and links with other control units during operation (not independent). In CAN communication, control units are connected with 2 communication lines (CAN H line, CAN L line) allowing a high rate of information transmission with less wiring. Each control unit transmits/receives data but selectively reads required data only.
CAN Communication Unit
TYPE 1
System diagram
Input/output signal chart
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TYPE 2
System diagram
Input/output signal chart
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