Anti-Slip Regulation System: How does the ASR work?

ESP warning light
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Anti-Slip Regulation (ASR) refers to the system designed to prevent slippage of the wheels, also known as the traction control system (TCS).

ASR is a device in the drivetrain that prevents the drive wheels from slipping at all speeds. This system extends the ABS (Anti-lock braking system) and ensures stability and controllability during acceleration.


How does the Anti-Slip Regulation System work?

During good road adhesion conditions, the engine power increases, and the car accelerates when the gas pedal is pressed. However, if the transmitted torque is higher than the wheel can transfer to the road or the road is slippery, the wheel will start to slip. If the wheels slip on only one side, the car will start to turn, which can be very dangerous.

In such cases, the ASR system begins to fulfill its function and thus reduces the torque transmitted to the wheel(s) that are slipping. Thus the car regains stability, and the wheel(s) stop spinning.

The ASR system can reduce torque transfer in three ways:

  1. Braking the skidding wheel - The first ASR systems mainly used this method.

  2. By interfering with the engine control unit (ECU) - For example, by reducing the amount of fuel or reducing the advance at a given moment.

  3. By combining both previous options.

Anti-Slip Regulation Warning Light

Vehicles with this system have a warning light on the dashboard, sometimes shared with the ESP warning light, which signals the status of the ASR system. After turning the key to the first position, the ASR warning light comes on briefly and then goes out, signaling that this system's functionality is being tested.

A constantly lit warning light indicates a malfunctioning wheel slip control system. Since the ASR system is classified as an active safety feature, most new modern cars are equipped with it. A malfunction of this system might light up the EPC warning light.

Video showcasing Anti-Slip Regulation System on and off: