check engine light Citroen DS4 DAG 2010.5 1.G Owner's Manual

271Practical information
The rear parking sensors will be deactivated automatically if a genuine
CITROËN towbar is used.
Driving advice
Distribution of loads
 Distribute the load in the trailer so that the heaviest items are as close as possible to the axle and the nose weight approaches the maximum permitted without exceeding it. Air density decreases with altitude, thus reducing engine per formance. Above 1 000 metres, the maximum towed load must be reduced by 10 % for every 1 000 metres of altitude. Refer to the "Technical Data" section for details of the weights and towed loads which apply to your vehicle.
Side wind
 Take into account the increased sensitivity to side wind.
Cooling
Towing a trailer on a slope increases the temperature of the coolant. As the fan is electrically controlled, its cooling capacity is not dependent on the engine speed.  To lower the engine speed, reduce your speed. The maximum towed load on a long incline depends on the gradient and the ambient temperature. In all cases, keep a check on the coolant temperature.
Braking
Towing a trailer increases the braking distance.
Tyres
 Check the tyre pressures of the towing vehicle and of the trailer, obser ving the recommended pressures.
Lighting
 Check the electrical lighting and signalling on the trailer.
 If the warning lamp and the STOP warning lamp come on, stop the vehicle and switch off
the engine as soon as possible.