Mercedes-Benz CLA Owner's Manual page 576

Display messages
Possible causes/consequences and
& WARNING Risk of an accident if the ball neck is not locked
If the ball neck is not in the locked position, the trailer may come loose.
Pull over and stop the vehicle safely as soon as possible, paying attention to road and traffic conditions.
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Do not continue driving under any circumstances.
Uncouple the trailer and secure it against rolling away.
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Initiate a new swivelling procedure and do not re-couple the trailer until the display message disappears.
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If the display message does not disappear, the trailer tow hitch is defective and the ball neck is not locked.
Do not couple up the trailer. Drive on without the trailer. Note the reduced ground clearance due to the
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unlocked ball neck.
Consult a qualified specialist workshop.
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The trailer tow hitch will not be operational when the vehicle is at a standstill.
Uncouple the coupled trailer and secure it against rolling away.
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Initiate a new swivelling procedure (
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If the ball neck is retracted: press and hold the button on the boot lid until the ball neck engages vertically in
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the locked position and then engages beneath the bumper.
If the ball neck is extended: press and hold the button on the boot lid until the ball neck engages beneath the
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bumper.
If the display message does not disappear, the trailer tow hitch is defective and the ball neck is not locked.
Display messages and warning/indicator lamps 573
M M Solutions
page 252).
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