Traction Control System (TCS)

DESCRIPTION - TRACTION CONTROL SYSTEM
Traction control reduces wheel slip and maintains traction at the driving wheels at speeds below 56 km/h (35 mph) when road surfaces are slippery. The traction control system reduces wheel slip by braking the wheel that is losing traction.

A Traction Control Off Switch that is a momentary contact type switch is located on the steering column upper shroud.

HYDRAULIC SHUTTLE VALVES
Two pressure relief hydraulic shuttle valves are included on vehicles with traction control. These valves are located inside the HCU and cannot be serviced separately from the HCU.

TRACTION CONTROL LAMP
The traction control function lamp is located in the transmission range indicator display of the instrument cluster.

OPERATION - TRACTION CONTROL SYSTEM
The traction control module monitors wheel speed. During acceleration, if the module detects front (drive) wheel slip and the brakes are not applied, the module enters traction control mode. Traction control operation proceeds in the following order:
1. Close the normally open isolation valves.
2. Start the pump/motor and supply volume and pressure to the front (drive) hydraulic circuit. (The pump/motor runs continuously during traction control operation.)
3. Open and close the build and decay valves to maintain minimum wheel slip and maximum traction.
The cycling of the build and decay valves during traction control is similar to that during antilock braking, except the valves work to control wheel spin by applying the brakes, whereas the ABS function is to control wheel skid by releasing the brakes.
If the brakes are applied at anytime during a traction control cycle, the brake lamp switch triggers the controller to switch off traction control.

HYDRAULIC SHUTTLE VALVES
Two pressure relief hydraulic shuttle valves allow pressure and volume to return to the master cylinder reservoir when not consumed by the build and decay valves. These valves are necessary because the pump/motor supplies more volume than the system requires.

TRACTION CONTROL LAMP
The traction control system is enabled at each ignition cycle. It may be turned off by depressing the Traction Control OFF Switch button when the ignition is in the ON position. The traction control function lamp illuminates immediately upon depressing the button.

The traction control function lamp illuminates during a traction control cycle.