312000895 - E2021 BRAKE LIGHTS - DESCRIPTION

DESCRIPTION

The vehicle brake lights are located at the rear in the side light clusters and in the special central third brake light and they consist of 5 bulbs.They are operated each time the brake pedal is pressed via the special switch on the pedal.

The switch fitted on the pedal unit consists of two contacts which supply two signals: the first is the N.O. type, which recognizes the position of the brake pedal if it is not in the rest postion, i.e. the pedal is pressed; the second is the N.C. type, which recognizes the position of the brake pedal in the rest position.

The lights are turned on by the N.O. contact (pedal pressed).The N.C. contact signal for the brake pedal is supplied to the engine management control unit which sends it, via the CAN, to the other network nodes.     See E5050 DIESEL ENGINES ELECTRONIC MANAGEMENT The control function is activated by the enablement signals (key ON) and the command from the switch contact.The engagement of the side brake lights is managed by the Body Computer, that of the third brake light is managed directly by the switch on the pedal.The correct operation of the side lights is controlled by the brake lights check function activated by the Body Computer and the following are monitored:

• open circuit (bulb missing or wiring interrupted);
• closed circuit to earth (bulb s.c. or wiring s.c. to earth);
• short circuit to battery voltage (wiring short circuited to Vbatt).

The electrical continuity of the fuse protecting the switch on the brake pedal is also checked.

The third brake light is not controlled by the check function.

When one of the situations described above is ascertained, the Body Computer makes the failure status available to the CAN: a special "general failure" warning light comes on in the instrument panel and, at the same time, the information is shown in the display.