ABS and EBD
See ABS and EBD
Front Brakes
See Front Brakes
Parking brake
See Parking brake
Rear wheel brakes
See Rear wheel brakes
Summary of the brake system
See Summary of the brake system
Scheme 129
Turbocharged gasoline engined cars with automatic transmission may start moving without throttle opening.
Braking in such circumstances by result in a reduced vacuum in the power brake booster.
To avoid this, an electronic accessory pump (3) is connected to the power brake booster via a T valve (5).
The electronic accessory pump (3), the vacuum control valve (4) and the pump relay (2) are positioned on a bracket under the left front fender.
The pump relay (2) is connected to the system relay (1) for the engine management system (EMS 2000).
The electronic accessory pump (3) activates if the vacuum in the power brake booster exceeds 40 kPa when the engine is running.
Note. When the ignition is on (engine not started) and a vacuum is requested, the electronic accessory pump (3) is activated and runs. The pump only runs for a few seconds because of the system relay (1).
The measurement range of the vacuum control valve (4) is 35 - 45 kPa
Reading off parameters
Note. The car should be driven to obtain the relevant values.
| No. | Parameter and status value | Remarks |
|---|---|---|
| 1 2 3 4 | SP LF SP RF SP LR SP RR km/h | Wheel speed left front wheel Wheel speed right front wheel Wheel speed left rear wheel Wheel speed right rear wheel Measurement range: 1.75-300 km/h The control module derives the wheel speed based on the signal from each wheel sensor |
| 5 | BRAKES ON/OFF | Status of the stop (brake) lamp switch. OFF= The stop (brake) lamp switch is not activated ON= The stop (brake) lamp switch is activated The signal from the stop (brake) lamp switch is used so that the control module is in standby mode for ABS control during braking. |
| 6 | PUMP MOTOR ON/OFF | Pump motor status OFF= The pump motor is not activated ON= The pump motor is activated |
| 7 | VALVE RELAY ON/OFF | Status of the valve relay in the control module OFF= The valve relay is not activated ON= The valve relay is activated The inlet and outlet valves are supplied with voltage when the valve relay is activated. |
Activating components/functions
Note. Activation can only be carried out if the vehicle speed is 0 km/h. The activation will be cancelled at higher speeds.
| No. | Component/function | Remarks |
|---|---|---|
| 1 | PUMP MOTOR | Activating the hydraulic modulator pump motor. Clearly audible noise from the ABS hydraulic modulator. Vibrations in the brake pedal when it is depressed. |
| 2 | OUTLET VALVE LF | Activating the outlet valve for the left front wheel. "Clicking sound" in the ABS hydraulic modulator. The valve opens the connection between the brake caliper and the low-pressure side of the pump. |
| 3 | INLET VALVE LF | Activating the inlet valve for the left front wheel. "Clicking sound" in the ABS hydraulic modulator. The valve closes the connection to the brake circuit. |
| 4 | OUTLET VALVE RF | Activating the outlet valve for the right front wheel. "Clicking sound" in the ABS hydraulic modulator. The valve opens the connection between the brake caliper and the low-pressure side of the pump. |
| 5 | INLET VALVE RF | Activating the inlet valve for the right front wheel. "Clicking sound" in the ABS hydraulic modulator. The valve closes the connection to the brake circuit. |
| 6 | OUTLET VALVE LR | Activating the outlet valve for the left rear wheel. "Clicking sound" in the ABS hydraulic modulator. The valve opens the connection between the brake caliper and the low-pressure side of the pump. |
| 7 | INLET VALVE LR | Activating the inlet valve for the left rear wheel. "Clicking sound" in the ABS hydraulic modulator. The valve closes the connection to the brake circuit. |
| 8 | OUTLET VALVE RR | Activating the outlet valve for the right rear wheel. "Clicking sound" in the ABS hydraulic modulator. The valve opens the connection between the brake caliper and the low-pressure side of the pump. |
| 9 | INLET VALVE RR | Activating the inlet valve for the right rear wheel. "Clicking sound" in the ABS hydraulic modulator. The valve closes the connection to the brake circuit. |