Traction Control System (TCS)

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 25 mph (40 km/h).

The control module monitors wheel speed. If during acceleration the module detects front (drive) wheel slip and the brakes are not applied, the control module will enter traction control mode. Traction control works in the following order when drive wheel slip is detected:

1. Close the (normally open) isolation valves.
2. Start pump/motor and supply volume/pressure to front hydraulic circuits (pump runs continuously during traction control).
3. Open and close build and decay valves to maintain minimum wheel slip and maximum traction.

The cycling of the build and decay valves works similar 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 pressure switch or brake switch will trigger the control module to switch off traction control. The LTCS function lamp will illuminate immediately upon entering traction control. 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 amber WARNING lamp will illuminate; however, a fault will not be registered.