841008463 - E7021 ASR / TCS DESCRIPTION (Automatic Transmission )

Description

The electronic anti-lock and anti-slip systems for the wheels regulates the braking pressure transmitted to the wheels, preventing them from losing grip whatever the tyre and road conditions. The function also controls the vehicle traction (ASR: Anti-Slip Reguation). intervening automatically any time one or both of the drive wheels are detected to be slipping.The system, managed by the braking control unit, has been designed to integrate and not to replace the conventional mechanical braking system, thereby offering the driver an effective safety device in the case of problems: the intervention takes place using the same brake fluid as in the regular mechanical braking circuit.Four sensors, located on each of the four wheels, signal the speed of each wheel to the electronic control unit, recording any situations involving locking, slipping or loss of grip.When these situations do occur, the braking control unit operates the solenoid valves which have the function of modulating the pressure in the hydraulic circuit, preventing locking and restoring the vehicle to the grip limit conditions; in this way the least possible braking distance is required without losing control of the steering.The sensors are the active type, i.e. they consist of a receiver and the magnetic codifier integrated in the hub bearing: in these conditions the signal is not affected by any interference of a magnetic nature or related to the temperature.In addition, the control unit manages the distribution of the braking load on the rear axle, replacing the mechanical brake distributor used previously (EBD function: Electronic Brake Distribution ).There is a specific control for deactivating the ASR function (but not the VDC system). The deactivating button and the warning light on the button are managed directly by the braking control unit.The braking control unit which manages the system is equipped with an autodiagnostic function: the moment an error or a fault is detected in the function, it deactivates the system immediately (if the vehicle is braked using the conventional system) and, at the same time, causes the warning light in the instrument panel to come on and the fault message is shown on the display.There is not a specific failure warning light for the ASR function in the instrument panel, therefore any system malfunction is signalled through the VDC warning light. When this warning light flashes, it also indicates the intervention of the ASR.If the control unit also detects an error in the EBD function, it operates the ABS failure warning light and also the insufficient brake fluid and handbrake applied warning light.The braking control unit calculates the speed of the vehicle starting from the figures that are supplied by the wheel sensors (with the control unit calculating the average value) and from the actual circumference of the wheels themselves, supplied by the Body Computer. this signal (speedometer signal) is then transmitted, via the CAN, to all the nodes that require this information for their functions.The braking control unit also produces a discreet signal which replicates the vehicle speed information calculated and transmitted via the CAN.The ASR system increases the active safety and stability of the vehicle controlling the slipping of the drive wheels: if the slipping is caused by the transmission of excessive power, the function intervenes (connected to the engine management control unit) reducing the power produced by the engine; if, on the other hand, the slipping is detected at one wheel only, the system intervenes braking that wheel only, acting on the modulating solenoid valve.The supply lines for the braking control unit are protected by two special maxifuses located inside the engine comparment junction unit; the supply controlled by the ignition (INT) comes from a specific fuse inside the dashboard control unit.