A fault associated with attaching a trailer should be assessed with both the vehicle installation and trailer considered. Working lamps do not prove that the entire towing interface and its electrical load are correct.
Record the combination
State whether the warning occurs with one trailer or several, and whether the vehicle behaves normally when disconnected. Include the towbar wiring-kit details, recent installation or repairs, and which lights or other functions fail. Do not assume that an aftermarket installation behaves like the factory arrangement.
Avoid homemade adapters or bridging terminals to suppress warnings. A qualified workshop should inspect the appropriate circuits and configuration. Send the complete scan and the sequence from connection to warning. If braking, lighting or vehicle stability is affected, stop towing and arrange assessment. The timing provides a useful starting point, but it does not prove that the body controller or gateway requires replacement.
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