A Traction Control System ( TCS ), also known as Anti-Slip Regulation ( ASR ), is typically (but not necessarily) a secondary function of the anti-lock braking system on production vehicles , and is designed to prevent loss of traction of the driven road wheels, and therefore maintain the control of the vehicle when excessive throttle is applied by the driver and the condition of the road surface (due to varying factors) is unable to cope with the torque applied.
The basic idea behind the need of a traction control system is the difference between the slips of different wheels or an apparent loss of road grip that may result in loss of steering control over the vehicle.
Difference in slip may occur due to turning of a vehicle or differently varying road conditions for different wheels. At high speeds, when a car tends to turn, its outer and inner wheels are subjected to different speed of rotation, that is conventionally controlled by using a differential .
A further enhancement of the differential is to employ an active differential that can vary the amount of power being delivered to outer and inner wheels according to the need (for example, if, while turning right, outward slip (equivalently saying, 'yaw') is sensed, active differential may deliver more power to the outer wheel, so as to minimize the yaw (that is basically the degree to which the front and rear wheels of a car are out of line.) Active-differential, in turn, is controlled by an assembly of electromechanical sensors collaborating with a traction control unit.
Imagine you are accelerating from a stop on an icy road in a front-wheel drive vehicle without Traction Control. If you accelerate very gently, you might be OK, but if you press the gas pedal just a bit harder, one or both front wheels could lose traction and begin to spin on ice, so the vehicle would be very hard to control.
The Traction Control is designed to help in a situation like this. Once the Traction Control System senses that any of the drive wheel(s) starts slipping, it reduces the engine torque and shortly applies the brake to the slipping wheel(s) to slow it down just enough to regain traction, thus helping you to control your vehicle during acceleration.
Typical Traction Control system is based on vehicle's Anti-lock braking system (ABS) and uses many of ABS components. It utilizes the ABS wheel speed sensors to monitor the speed of all four wheels.
When Traction Control system senses that the wheel looses traction (begins to rotate faster) during acceleration, it applies the brakes to that wheel using the ABS hydraulic module and commands the Engine Control Module to reduce the engine power. When Traction Control system operates, you could probably feel that the engine power is reduced and hear some buzzing noise similar to that of ABS. The Traction Control light may also flash.