System Description

SYSTEM DESCRIPTION AND FUNCTIONAL OPERATION

TEVES MARK20e SYSTEM DESCRIPTION
The controller antilock brake module is used to monitor wheel speeds and to modulate (control) hydraulic pressure in each brake channel. The modulated hydraulic pressure is used to prevent wheel lock-up during braking.

The Teves Mark20e system uses a diagonal split hydraulic brake system. In the standard brake mode the master cylinder primary circuit supplies pressure to the right front and left rear wheel brakes, and the secondary master cylinder circuit supplies pressure to the left front and right rear wheel brakes.

All vehicles equipped with ABS use Electronic Variable Brake Proportioning (EVBP) to balance front-to-rear braking when brakes are applied in the partial braking range.

During an antilock stop the Mark20e system uses four-channel operation. This means that during antilock operation each wheel brake is independently controlled. By using a separate hydraulic channel for each wheel, the system is able to retain directional stability and steering control while applying maximum braking. The system provides maximum braking even when road conditions vary.

TRACTION CONTROL SYSTEM (TCS) DESCRIPTION (IF EQUIPPED)
The Traction Control System is available on this vehicle. The main purpose of traction control is to reduce wheel slip and maintain traction at the driven wheels when road surfaces are wet or snow covered. The traction control system reduces wheel slip by braking the wheel that is losing traction. The system is designed to operate at speeds below 56 km/h (35 mph).

The Controller Antilock Brake (CAB) monitors wheel speed. If during acceleration the CAB detects front (drive) wheel slip and the brakes are not applied, it will enter traction control mode. The CAB performs the traction control function in the following sequence:
1. Closes the (normally open) isolation valves.
2. Starts pump/motor to supply volume/pressure to front hydraulic circuits (pump runs continuously during traction control).
3. Opens and closes build and decay valves to maintain minimum wheel slip and maximum traction.

The cycling of the build and decay valves works similarly to ABS except that they work to control wheel spin by applying brakes. ABS function is to control wheel skid by releasing brakes.

Two pressure relief valves allow pressure/volume to return to the reservoir when not consumed by the build/decay cycles. These are required because the pump supplies more volume than the system requires. -

If at any time the brakes are applied during a traction control cycle, the brake switch will trigger the CAB to switch off the traction control.

The traction control system will be enabled at each ignition cycle. It may be turned off by depressing the traction control switch. The traction control system function indicator will illuminate immediately upon depressing the traction control switch button. The indicator will flash during a traction control cycle. If the controller calculates that the brake temperatures are high, the traction control system will become inoperative until a time-out period has elapsed. When in this thermo protection mode, the traction control indicator will illuminate; however, a fault will not be registered.