ASR: definition, function, operating principle, and causes of failure

ASR: definition, function, operating principle, and causes of failure

ASR is an electrohydraulic active safety system that prevents wheel slippage. It is installed on Audi, Peugeot, Fiat, Renault, Seat, Volkswagen, and other cars. It improves road grip and reduces the load on transmission when driving off-road. This system ensures reliable starts on wet or icy surfaces and improves the handling of a vehicle when driving uphill.

How ASR works

The system constantly monitors the speed at which the wheels rotate and compares the measurements it receives. This data comes from the ABS sensors. If this data indicates that a wheel is slipping, braking force is applied to that wheel. This is done by means of a brake fluid return pump and additional solenoid valves. These valves and pump co-operate to build up and adjust the pressure in the brake circuits. In addition, the engine torque can be reduced until traction is restored.

ASR can be turned off using a button on the centre console. This can sometimes be helpful for negotiating sections of road with fresh snowfall. In this case, ASR doesn’t limit the engine speed when the accelerator pedal is pressed.

Popular cars equipped with ASR

  • Audi A6 C5, A2 8ZO, A4 В6;
  • Peugeot 3008 I, 207;
  • Fiat Doblo I, II, Stilo;
  • Renault Megane III, Scenic II;
  • Seat Leon FR Mk3;
  • Volkswagen Golf V, Volkswagen Transporter T5.

Causes of ASR malfunctions

  • Ignition coil failure.
  • Damage to the high-voltage wires.
  • Throttle body malfunctions.
  • Soiled ABS sensors or breakage of their wires.
  • Low brake fluid level.
  • Poor contact in a relay.
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