Volvo XC90: Starting and driving / Trailer Stability Assist

(Option/accessory.)

Trailer Stability Assist (TSA¹) is part of the ESC² stability system and is a function designed to help stabilize a vehicle that is towing a trailer when the vehicle and trailer have begun to sway. The function is added when installing a towbar. Contact a Volvo retailer for more information.

Reasons for swaying

A vehicle towing a trailer may begin to sway for various reasons. Normally this only occurs at high speeds. However, if the trailer is overloaded or unevenly distributed, e.g. too far back, there is a risk of swaying even at low speeds.

Swaying may be caused by factors such as:

• The vehicle and trailer are hit by a sudden, strong crosswind.
• The vehicle and trailer are traveling on an uneven road or over a bump.
• Sudden movements of the steering wheel.

Once swaying has begun, it can be difficult or impossible to stop it. This makes the vehicle and trailer difficult to control and there is a risk of swerving into oncoming traffic or driving off the road.

Trailer Stability Assist function

Trailer Stability Assist continuously monitors the vehicle's movements, particularly lateral movements. If swaying is detected, the brakes are applied individually on the front wheels, which has a stabilizing effect on the vehicle and trailer. This is often enough to enable the driver to regain control of the vehicle.

If the Trailer Stability Assist function's first attempt is not adequate to stop the swaying motion, the brakes are applied on all wheels and engine power is temporarily reduced. As the swaying motion begins to decrease and the vehicle and trailer have once again become stable, TSA stops regulating the brakes/engine power and the driver regains control of the vehicle.

NOTE

Trailer Stability Assist is deactivated if the driver activates ESC Sport Mode in the center display's menu system.

Trailer Stability Assist may not intervene if the driver tries to compensate for the swaying motion by moving the steering wheel rapidly, because the system will then not be able to determine if it is the trailer or the driver causing the swaying.

When Trailer Stability Assist is activated, the ESC symbol is displayed in the instrument panel.

NOTE

A vehicle software update is required when a towbar is retrofitted. Contact a Volvo retailer.

¹ Trailer Stability Assist

² Electronic Stability Control