Description The electronic anti-lock brake system ( BOSCH 8.0 ABS) governs braking pressure sent to the wheels and prevents loss of grip under all tyre and road surface conditions.The system is designed to be integrated with the braking system (using the same hydraulic fluid) without preventing the operation of the braking system if the operation of the ABS fails.Four sensors fitted to the four wheels inform the electronic control unit of wheel speed at every moment. In this way, they detect wheel lock, wheel slip and loss of grip.Under these conditions, the control unit sends specific instructions to solenoids that modulate hydraulic circuit pressure to eliminate lock and restore the car to within grip limits which allows optimum driveability and stopping distances.The sensors are the 'active' type, i.e. supplied by the control unit; they consist of a receiver that faces a magnetic coding device built into the hub bearing so that the signal is less influenced by electromagnetic interference and variations in temperature.The ABS control unit also controls brake force distribution of the rear axle in relation to the front axle, allowing the mechanical load proportioning device used previously to be dispensed with (EBD function: Electronic Brake Distribution).The control unit is equipped with a self-diagnostic function: when an error is detected in the ABS function the warning light comes on and the system is simultaneously deactivated; Under these conditions, the car brakes using only the conventional system.When the control unit detects an error which also affects the operation of the EBD logic, the 'ABS failure' warning light and the 'insufficient brake fluid level' and 'handbrake applied' warning light comes on.23
23Under these conditions, the rear brake distribution control is also deactivated: the customer must therefore drive very carefully to the first service centre.
23The general failure warning light comes on if the instrument panel detects an ABS failure warning light fault. For more details 2398688Characteristic of working principle3340A(B.S. ANTI-LOCK BRAKING SYSTEM .) . The ABS control unit computes vehicle speed on the basis of values supplied by drive wheel sensors (the ABS control unit computes an average reading) and true wheel circumference supplied by the body computer. This speed signal is then sent to nodes that require the information via the CAN network. The ABS control unit also generates a discrete signal that copies the vehicle speed information computed and transmitted via the CAN network.The control unit supply lines are protected by a special maxifuse located in the engine bay control unit. ignition-operated power supply from a special fuse in the underfacia control unit.
Functional description The ABS electronic control unit M50 is supplied (at pin 2 and 3) directly by the battery via a line protected by maxifuse F5, housed in the engine compartment junction unit B1. The ignition-operated supply (INT/A) reaches pin 18 from the line protected by the fuse F42 of under facia control unit B2.The control unit is earthed at pins 1 and 4. The four sensors K70, K71, K75, K76 send wheel speed signals to pins 15-16, 10-9, 17-6 and 19-8 of M50 respectively. Brake pedal switch I30 sends an enablement signal to pin 20 of control unit M50: the ABS cannot intervene unless the brake pedal is pressed. The switch I30 is supplied when the ignition is switched on (INT) from fuse F37 of junction unit B2 . Pin 23 di M50 emits a discrete speed signal that is sent tol Body Computer M1; the same signal is also copied via the CAN network. Pins 15 and 26 of ABS control unit M50 connect to engine management control unit M10, Body Computer M1 and instrument panel E50, via the CAN line, to control the ABS failure warning light; if the problems involve the EBD function, the insufficient brake fluid and handbrake applied warning light comes on in addition to the ABS failure warning light. If the instrument panel detects a fault in the ABS failure warning light, the general failure warning light is lit up. Self-diagnostic data can be read by connecting to connector C of Body Computer M1- pin 1: it receives signals from pin 11 of the control unit M50 via the special diagnostic line.2399396SeeE8010DIAGNOSTIC MULTIPLE CONNECTOR
<anchor>0</anchor><span>Removing</span><icon><imageid>20</imageid></icon>1Refitting21Open the bonnet lid and disconnectthe battery.1. Undo the nut.2. Move aside the retainer.3. Remove the battery carefully.2050795
5530B22
<anchor>0</anchor><span>Removing</span><icon><imageid>20</imageid></icon>1Refitting212400577-5530B10battery - r+r2400580-5530B52Battery DRIP TRAY/SUPPORT - R.R.Open the bonnet lid.1. Disconnect the electrical connection (1a) from the negative batteryterminal (1b).2. Disconnect the electrical connection from the bodyshell3. Disconnect the electrical connection from the gearbox casing.4. Keep the battery earth lead.2050796
5530B36
<anchor>0</anchor><span>Removing</span><icon><imageid>20</imageid></icon>1Refitting21Place the vehicle on a lift.Raise the car.1. Undo the nut (1a) and disconnect the electrical connections (1b,1c) from the starter motor.2050797
5530B52
<anchor>0</anchor><span>Removing</span><icon><imageid>20</imageid></icon>1Refitting212400577-5530B10battery - r+r1. Open the retaining bands and release the wiring.2. Remove the battery support tray (2a), releasing the dischargepipe (2b) from the passage hole (2c). 3. Undo the bolts.4. Remove the battery cage.2050799
5530B60
<anchor>0</anchor><span>Removing</span><icon><imageid>20</imageid></icon>1Refitting21Open the bonnet lid.1. Undo the nut.2. Undo the retaining buttons using the special tool3. Remove the belt.2050800
<anchor>0</anchor><span>Removing</span><icon><imageid>20</imageid></icon>1Refitting21Open the bonnet lid.1. Release the retainers (1a) and remove the cover (1b).2050746
<anchor>0</anchor><span>Removing</span><icon><imageid>20</imageid></icon>1Refitting212400802-7040A37fuse box cover - r r1. Disconnect the electrical connections (1a, 1b, 1c, 1d, 1e, 1f).2. Undo the bracket retaining bolt.3. Slightly move the bracket (3a) for the dashboard trim and undothe bolt (3b).4. Undo the other bolts securing the body computer/junction unit.5. Slightly move the body computer/junction unit assembly.6. Disconnect the electrical connections (6a, 6b, 6c).7. Recover the body computer/junction unit.2050752
<anchor>0</anchor><span>Removing</span><icon><imageid>20</imageid></icon>1Refitting211. Disconnect electronic control unit electrical connections (1a),(1b), (1c).2. Undo the bolts.3. Recover the control unit.2050753
<anchor>0</anchor><span>Removing</span><icon><imageid>20</imageid></icon>1Refitting211. Disconnect electronic control unit electrical connections (1a),(1b), (1c).2. Undo the bolts.3. Recover the control unit.2050754
<anchor>0</anchor><span>Removing</span><icon><imageid>20</imageid></icon>1Refitting21 Proceed with removal 2400577-5530B10battery - r+r1. Remove the protective cap on the brake caliper bleed valve. 2. Connect the collection system (pipe and reservoir) to the bleedvalve on the brake caliper. 3. Loosen the bleed valve on the brake caliperWait for the brake-clutch reservoir todrain.2050481
3340A13
<anchor>0</anchor><span>Removing</span><icon><imageid>20</imageid></icon>1Refitting21 Proceed with removal 2400577-5530B10battery - r+r Proceed with removal 2400367-3340A12A'B.S. system. - electronicand hydraulic CONTROL UNIT R.R.1. Release the right brake pipe from the band on the A.B.S. controlunit mounting.2. Undo the nuts (2a) and the bolt (2b) and remove the A.B.S. controlunit mounting (2c).2050485
3340A20
<anchor>0</anchor><span>Removing</span><icon><imageid>20</imageid></icon>1Refitting2123-. For versions with ESP, theA.B.S. electronic control unit is handled individually by the Parts Department,but supplied together with the hydraulic control unit. Proceed with removal 2400577-5530B10battery - r+r Proceed with removal 2400367-3340A12A'B.S. system. - electronicand hydraulic CONTROL UNIT R.R.1. Undo the bolts (1a) and separate ABS electronic control unt (1b)from the hydraulic assembly.2050486
<anchor>0</anchor><span>Removing</span><icon><imageid>20</imageid></icon>1Refitting21.23The following procedure describesremoval/refitting of the left rear wheel rpm sensor; proceed asfor the right rear wheel rpm sensor.Position the vehicle on the rampEnsure that the ignition key is in theOFF position, then disconnect the negative battery terminal (-). 1. Undo the bolt (1a) and remove the rear wheel rpm sensor (1b).2. Release the rear wheel rpm sensor electrical wiring from theattachments on the rear suspension.2050491
