General description

GENERAL DESCRIPTION

The electronic system controlling the suspension varies the setting of the four shock absorbers, in real time, on the basis of the variations in driving and road conditions detected by the relevant sensors. This means that road holding and comfort are greatly increased.

Depending on the choice of the driver, the system operates with two different intervention procedures:

• "AUTO" which entrusts the control of the shock absorbers to the electronic system under all driving conditions;
• "SPORT" which locks the setting to "rigid" permitting high performance sports driving

The choice between the two possibilities is made by acting on one of two buttons located on the relative control panel B67 equipped with leds which signal the selected option.

PRINCIPLES OF OPERATION:

The electronic control unit N48 varies the setting of the suspension by acting on solenoid valves M17-M18-M19-M20 which adjust the flow of oil within the shock absorbers.

The rigidity varies in relation to the speed of the vehicle, detected by the speedometer sensor L17.

At extremely low speed (below approximately 5 km/h) the setting remains rigid, thus avoiding excessive springiness during manoeuvring or when driving on rough roads. For speeds up to approximately 30 km/h the soft setting of the steering is employed ensuring ease of driving and greater comfort, while a rigid setting controls accelerating and braking.

At higher speeds the system changes the rigidity when one of the sensors signals particular road or driving conditions, for example:

• sudden changes in direction or light bends, through the steering angle sensor L40, which measures angles and speed of rotation of the steering wheel;
• bumps or roughness through the accelerometer N47 which detects relevant vertical accelerations;
• sudden braking detected by the brake fluid pressure switch L41, which intervenes when the pressure of the brake fluid is higher than 20 bars;
• increasing speed, detected by the speedometer sensor L17, increases the rigidity of the system (above 150 km/h, for example. It is rigid under all conditions).

FUNCTIOnAL DESCRIPTION

The system is controlled by the control unit N48, located under the rear seat. The supply to the control unit is key-operated via fuse F17 (7.5 A) in fusebox G1.

The same line also supplies the control panel B67, which is in addition connected to the sidelights circuit so that the control panel is lit.

This is connected via four signals to the control unit: an ground signal (from pin 2 for the "AUTO" logic, from pin 5 for the "SPORT" logic) is sent to the control unit when the switch of the chosen option is pressed, which informs the control unit. A "feed-back" signal (at pin 6 or 7) lights up the relative warning lamp.

A specific line connects the control unit to the instrument panel C10 (pin 3 of connector D) to which the processed malfunction signal is sent by the self-diagnosis function.

The control unit is also connected with three signals at the connector for the system diagnosis T1. The control unit receives signals from the sensors to which it is directly connected;

• three signals from the steering angle sensor L40: three leds and three photoconductive diodes measure the steering angles and transform them into impulses; the first signal (STR-Z), from pin 1B, indicates rectilinear direction and the others (STR1 and STR2), from pins 2B and 3B, send an impulse approximately every 18° of steering angle spread so that the control unit is signalled each 9°. Power supply and ground reach pins 2A and 1A respectively of the sensor.

SELF-DIAGNOSIS:

The system automatically and continuously controls its own operation (self-diagnosis): any anomalies which are picked up, are signalled by the control unit via the relative warning lamp located on the instrument panel and, at the same time, the system is set to the "rigid" position whatever the option selected. The warning light will stay on, as long as the key is in the ignition, until the fault has been rectified.

It will therefore be necessary to carry out the troubleshooting as indicated below. An electronic diagnosis is also possible by connecting connector T1 to the ALFA ROMEO Tester.

During starting the warning light comes on for 2 - 3 seconds, then, if no malfunctions have been detected, it goes out. This makes it possible to easily check the correct operation of the system.