2.4. When a tractor is equipped with
an electric control line and electrically connected to a towed vehic
le equipped with an electric control
line, a continuous failure (> 40 ms) within the electric control
line shall be detected in the tractor and shall be signalled to the driver by the yellow warning
signal specified in point 2.2.1.29.1.2 of Annex I, when such vehicles are connected via the electric control
line ...[+++].