The Ducati ABS brake system manages the front and rear brakes separately. A pulse generator (phonic wheel), with a ring of slots, is fixed onto each wheel. On the left calliper mounting bracket of the front fork and on the rear brake calliper holder plate are HALL effect sensors which detect the full sections and voids on the phonic wheel as the vehicle moves, providing and in­stantaneous wheel speed reading. These sensors transmit the data to the ABS control unit, which contains software implement­ing a specific control algorithm developed by Ducati. The software compares the average speed of the vehicle against the instantaneous wheel speed values to determine the degree of skidding. If the pressure applied to the calliper by the rider causes the control limits to be exceeded, the control unit intervenes in the braking circuit relative to the wheel for which incipient lock-up is detected. The ABS modulates the calliper pressure with a system of solenoid valves that initially prevents any further in­crease in hydraulic pressure (EV valve closed), and then reduces pressure (AV valve opened). The AV valve is opened in a series of pulses (with less than 10 milliseconds between successive pulses), to reduce pressure in steps. When the wheel begins to rotate again in response to the diminished braking force applied and the wheel speed reaches the reference value, the AV release valve is closed.

Simultaneously, the EV inlet valve is reopened, restoring normal operation of the brake system. The ABS control unit can monitor and modulate brake force accordingly in the three following different conditions: dry road surface (high grip), wet or greasy road surface (poor grip) and uneven road surface. ABS functionality is disabled at vehicle speeds lower than 5 km/h.

The hydraulic component of the ABS system consists of a primary circuit (from the pump to the control unit and from the control unit to the calliper) and a secondary circuit (completely within the control unit). The hydraulic layout of the ABS system is given below.

The response of the system is based on the analysis of the speed signals for front and rear wheels; the system is automatically deactivated if either of these signals is missing.

In the event of the ABS control unit detecting a fault in the ABS electronic management system, it activates the specific fault warning indicator on the instrument panel and restores conventional braking functionality without ABS.

Hydraulic faults in the brake system and faults not directly related to the ABS system (e.g.: worn brake pads) cannot be detected by the ABS control unit.

The response of the system is based on the values read for the front and rear wheel speeds; take great care not to damage the phonic wheels and relative speed sensors when removing the wheels or when working in the vicinity of these components; dam­age to the phonic wheels damages may compromise the operation of the system and cause dangerous malfunctions.

The diagnostic function of the ABS 8M ascertains the functionality of the main system components via hardware/software tests, but cannot modify the operating parameters of the ABS system. The DDS diagnostic instrument is connected by cable to the ABS control unit communication link connector (A), located beneath the saddle. The connection cable between the tester and the ABS control unit has another branch with a negative and a positive clamp that must be connected to the vehicle battery to power the tester itself and enable communication with the ABS control unit.

From the SELF-DIAGNOSIS menu of the DDS instrument, select the ABS system model and wait until the correct configuration loads for analysing the configuration of the vehicle. After switching the vehicle to key-on state, the tester communicates with the ABS control unit.

Once in this configuration, a number of parameters and states relative to the ABS control unit and information concerning the control unit itself may be selected and displayed.

If the tester receives notification from the ABS control unit that there are diagnostic errors dating from a prior test session still stored in its memory, the user is warned by specific message on the display and an audible alarm.

This tester function provided the user with information concerning the error list in the ABS control unit memory, indicating if er­rors have been stored previously stored or if they are current. The following codes are given after a short description of the diag­nosis type: MEM, indicating that the error has been stored previously by the ABS control unit but has not been detected in the current test session. ATT, indicating that the error is current and has been detected during the current test session.

While ATT indicates that the error has been diagnosed during the current test session, it does not necessarily indicate that the error is actually active at the time of indication. For example: disconnecting the front wheel speed sensor causes the code ATT to be displayed after the error description, but the code continues to be displayed even once the cause of its activation has been eliminated by reconnecting the sensor, as the ABS will only check sensor operation again after the next key-off/key-on cycle. As a result, always perform a key-on/key-off cycle after any work on the ABS system, interrupting and reopening communication between the diagnostic instrument and the ABS control unit before checking the updated ABS error list again.

This tester function displays the identification data for the ABS system, such as Supplier reference, Software version and BAR­CODE.

Carry out the procedure described in section 6 - 5, ABS disabling function.

If the vehicle front wheel remains off the ground for a prolonged period while the vehicle is in motion, the speed difference de­tected between the two wheels causes an ABS fault (warning light activated) and makes it impossible for the control unit to es­tablish a reference speed.