ETS control mode, function

The "Electronic Traction System" (ETS) is an automatic system for improving the vehicle's moving-off and acceleration capabilities on road surfaces with different degrees of grip within a specified speed range (0 to max. 40 km/h). Wheel spin is limited by means of intervention by the brake system.

The ABS control module (A2) registers and processes the rotational speeds of all wheels. If the ABS control module (A2) recognizes from the wheel speed signals that one of the drive wheels (or both when cornering) tends to spin, ETS control mode commences.

ETS control mode operates in 2 distinct control ranges:

Control mode for one-sided brake intervention

The spinning wheel is braked by the appropriate wheel brake until the calculated drive slip is obtained. The other wheel can now transmit a drive torque that is higher by the amount of the braking torque (differential lock effect).

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If this differential lock effect results in so much drive torque being transmitted to the wheel with the higher friction coefficient that this wheel also starts to spin, then the braking torque on the spinning wheel is canceled.

Solenoid valves in the hydraulic unit regulate the braking torque with pressure build-up, pressure hold and pressure reduction phases.

Control mode for brake intervention on both sides (cornering)

If both drive wheels spin while cornering within a specified speed range, then both drive wheels are braked to prevent the vehicle from breaking away.

Brake intervention on both sides is also regulated with pressure build-up, pressure hold and pressure reduction phases.

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Signaling devices

A warning lamp (hazard warning triangle in the instrument cluster) indicates a difference between the wheel speed and the vehicle speed. It thus warns the driver that his vehicle is approaching its physical limits.

If a fault occurs in the system, the lamp with the inscription "ETS" or with a symbol denoting a rolling tire is switched on.