How Traction Control Reacts to Road Conditions
The traction control system (TCS) prevents wheels from losing traction when the engine delivers torque (when you push the throttle). Traction loss is when there is no grip between a tire and the road surface. The wheel slips on a low grip surface and spins faster than other wheels.
The next question is, “How does the TCS detect [traction loss] and adjust the [tire] speed?” Sensors measure the rotational speed of the four wheels and the global speed of the vehicle. The speed data is constantly monitored by the Electrical Control Unit (ECU). When the ECU detects from the sensors’ data that a wheel is rotating faster than the three other wheels, which is equal to the vehicle’s speed, then it means it is slipping. The ECU then outputs a signal to activate the brakes in brief successions to adjust the speed or by reducing the torque output from the engine.
One of the limits of the TCS is when all four wheels are slipping in a standstill position. The system doesn’t understand because all wheels don’t match the vehicle’s speed. The system thus kicks in and reduces torque output from the engine too much. In this case, car manufacturers generally recommend turning off the TCS.