- when the ignition is switched on, the self-diagnosis lamp lights up. When the engine is running, it goes out if all the lamps are working;
- if the control lamp is on when the engine is running, one of the lamps has burned out;
- the control lamp lights up only when the device is turned on with a faulty lamp;
- if the brake signal lamp burns out, the control lamp will light up when braking and go out when the ignition is turned off;
- the trailer socket must be connected according to the diagram.