Traction Control System, or TCS

A traction control system (TCS), also known as Anti-Slip Regulation (ASR), on current production vehicles, are typically (but not necessarily) electro-hydraulic systems, designed to prevent loss of traction of the driven road wheels, and therefore 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. Although similar to electronic stability control (ESC) systems, traction control systems do not have the same goal.

The intervention can consist of any, or all, of the following:
Retard or suppress the spark to one or more cylinders
Reduce fuel supply to one or more cylinders
Brake one or more wheels
Close the throttle, if the vehicle is fitted with drive by wire throttle.
In turbo-charged vehicles, the boost control solenoid can be actuated to reduce boost and therefore engine power.

Typically, the traction control system shares the electro-hydraulic brake actuator (but does not use the conventional master cylinder and servo), and the wheel speed sensors with the anti-lock braking system.
Traction Control System, or TCS, was well intentioned but didn't necessarily work out well. For one thing, it tends to be a ruthless dictator that often overrides the turbocharger's ability and the driver's desires. There's a really dark side beyond that though: If any part of this complex system fails, the whole system goes into limp-home mode. Limp-home mode is exactly what it sounds like: You have just enough power to get the car home or to the nearest garage, and that's all. If you're in the middle of nowhere, that isn't pleasant. If you're making a left hand turn in heavy traffic and it goes into limp-home mode, you're in deep ... well, let's just call it deep trouble. And once it goes into this mode, the car is pretty much useless until the problem is diagnosed and corrected - you might get it home, but then you have to fix it before you can resume daily driving. And guess what? That can get real, REAL expensive.