Trailer stability assist*

The function of trailer stability assist (TSA1) is to stabilise cars towing trailers in situations where they begin snaking. The function is included in the stability system ESC2.

Reasons for snaking

The snaking phenomenon can occur with any car/trailer combination. Snaking normally occurs at high speeds. However, there is a risk of it occurring at lower speeds if the trailer is overloaded or the load is improperly distributed, e.g. too far back.

In order for snaking to occur, there must be a triggering factor, e.g.:

  • Car with trailer subjected to a sudden and powerful side wind.
  • Car with trailer drives on an uneven road surface or in a pothole.
  • Sweeping steering wheel movements.

If snaking has started, it could be difficult or even impossible to suppress. This makes the car/trailer combination difficult to control and there is a risk that you could, for example, end up in the wrong lane or leave the carriageway.

Trailer stability assist function

The trailer stability assist function continually monitors the car's movements, particularly lateral movements. If snaking is detected, the front wheels are individually braked. This serves to stabilise the car/trailer combination. This is often enough to help the driver regain control of the car.

If snaking is not eliminated the first time that trailer stability assist intervenes, the car/trailer combination is braked with all wheels and engine power is reduced. Once snaking has been gradually suppressed and the car/trailer combination is stable once again, the system stops regulating and the driver once again has full control of the car.


The stability function is deactivated if the driver selects Sport mode by deactivating ESC via the menu system in the centre display.

Trailer stability assist may fail to intervene if the driver uses severe steering wheel movements to try to rectify the snaking because in such a situation the system cannot determine whether it is the trailer or the driver causing the snaking.

P5-1507-Symbol-ESC 19x19

When Trailer Stability Assist (TSA) is operating, the ESC symbol flashes in the driver display.

  1. * Option/accessory.
  2. 1 Trailer Stability Assist
  3. 2 Electronic Stability Control