Editing Traction control system (section)

{{Short description|Function of the electronic stability control on production motor vehicles}}
{{Refimprove|date=January 2010}}
A '''traction control system''' ('''TCS'''), is typically (but not necessarily) a secondary function of the [[electronic stability control]] (ESC) on production [[motor vehicle]]s, designed to prevent loss of [[traction (engineering)|traction]] (i.e., [[wheelspin]]) of the driven road wheels. TCS is activated when [[throttle]] input and [[engine power]] and [[torque]] transfer are mismatched to the road surface conditions. 

The intervention consists of one or more of the following:
*Brake force applied to one or more wheels
*Reduction or suppression of spark sequence to one or more [[cylinder (engine)|cylinder]]s
*Reduction of fuel supply to one or more cylinders
*Closing the throttle, if the vehicle is fitted with [[drive by wire]] throttle
*In [[Turbocharger|turbocharged]] vehicles, a boost control solenoid is actuated to reduce boost and therefore engine power.

Typically, traction control systems share the [[Electrohydraulic servo valve|electrohydraulic]] brake [[actuator]] (which does not use the conventional master cylinder and servo) and wheel-speed [[sensor]]s with [[Anti-lock braking system|ABS]].

The basic idea behind the need for a traction control system is the loss of road grip can compromise steering control and stability of vehicles. This is the result of the difference in traction of the drive wheels. The difference in slip may occur due to the turning of a vehicle or varying road conditions for different wheels. When a car turns, its outer and inner wheels rotate at different speeds; this is conventionally controlled by using a [[Differential (mechanical device)|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 as needed. For example, if outward slip is sensed while turning, the active differential may deliver more power to the outer wheel in order to minimize the [[Yaw (rotation)|yaw]] (essentially 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.