ABS system operation information
The operation 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.
Note
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.
Important
The operation 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 close to these components; the phonic wheels damage may compromise the operation of the system and cause dangerous malfunctions.
ABS diagnosis
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 socket (A), located beneath the seat. 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 of 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 or current test session still stored in its memory, the user is warned by specific message on the display and an audible alarm.
The ABS control unit identification number, identified by the prefix ID ECU, may be viewed from the INFO menu.
Select the function “View parameters and states”
This function allows the tester to display the following ABS system parameters and states:
Viewable parameters
 
Front wheel speed
 
The speed value for the front wheel is displayed in Km/h.
 
Rear wheel speed
 
The speed value for the rear wheel is displayed in Km/h.
 
System voltage value
 
The system voltage value, measured across the terminals of the ABS unit, is displayed in Volts
Viewable states
 
Hydraulic pump motor state
 
Indicates if the electric motor of the hydraulic pump inside the ABS unit is functioning or not.
 
Valve relay state
 
Displays the state of the main valve relay inside the ABS unit.
 
Rear inlet valve state
 
Displays the state of the normally open EV1 rear inlet valve (OFF if open, ON if closed).
 
Front inlet valve state
 
Displays the state of the normally open EV4 rear inlet valve (OFF if open, ON if closed)
 
Front outlet valve state
 
Displays the state of the normally closed AV4 rear outlet valve (OFF if closed, ON if open).
 
ABS switch state
 
Displays state of the analogue input of the ABS unit for the strategy switch off request (1 state to Uz, 0 state to GND).
Select the function “View errors”
This tester function provides the user with information concerning the error list in the ABS control unit memory, indicating if errors are stored or 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.
Note
While ATT indicates that the error has been found 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 re-establishing communication between the diagnostic instrument and the ABS control unit before checking the updated ABS error list again.
The abbreviations for all the errors displayed are given as follows:
 
Errors
 
Description
 
Front speed sensor signal
 
Open circuit/short circuit to GND/short circuit to Uz of rear wheel speed sensor
 
Front speed sensor signal - Plausibility
 
Front speed sensor fault - Plausibility
 
Rear speed sensor signal
 
Open circuit/short circuit to GND/short circuit to Uz of front wheel speed sensor
 
Rear speed sensor signal - Plausibility
 
Rear speed sensor fault - Plausibility
 
Plausibility of difference between front and rear wheel speeds
 
Front and rear wheel speed difference (WSS_GENERIC)
 
Front inlet valve fault
 
Front inlet valve (EV) fault
 
Rear outlet valve fault
 
Rear outlet valve (AV) fault
 
Rear inlet valve fault
 
Rear inlet valve (EV) fault
 
Front outlet valve fault
 
Front outlet valve (AV) fault
 
ABS pump fault
 
ABS pump motor fault
 
Valve relay fault
 
Valve relay fault (Failsafe relay)
 
ABS electronic control unit fault
 
ECU fault
 
ABS unit power circuit fault
 
ABS power circuit fault
Select the function “ABS system information”
This tester function displays the identification data for the ABS system, such as Supplier reference, Software version and BARCODE.
e.g.:
Supplier ref.: DUCM696
Software version: 67890
Bar Code Data: HQOJM98200RA