148 Driving and operatingLock coupling ball bar by turning thesupplied key in the lock cylinder of thecoupling ball bar. Remove key.Check that the coupling ball bar iscorrectly attached:■ Green marking must be visible onlever.■ Coupling ball bar must be seatedfirmly in coupling housing.Coupling ball bar must be locked andkey must be removed.9 WarningTowing a trailer is permitted onlywhen the coupling ball bar is fittedcorrectly. If the coupling ball barcannot be properly attached, seekthe assistance of a workshop.Eye for break-away stopping cableIn the case of trailers with brakes,attach the break-away stopping cableto the eye - not to the coupling ballbar.Dismounting the coupling ball barUnlock coupling ball bar and removekey. Push lever to the left, towards thecoupling ball bar and turn itdownwards. Pull coupling ball bar outof coupling housing.Remove any rust or dirt from areaaround the coupling housing andcoupling ball bar connection beforeinserting sealing plug in the hole.Place the coupling ball bar in the bagsupplied, fasten it with the strap andstow it below the floor cover in theload compartment.Do not use steam-jet cleaners orother high-pressure cleaners to cleanthe coupling ball bar.Trailer stability assistIf the system detects snakingmovements, engine power is reducedand the vehicle/trailer combination isselectively braked until the snakingceases. While system is working keepsteering wheel as still as possible.Trailer stability assist (TSA) is afunction of the Electronic StabilityControl 3 137.
