Parking Brake

Parking Brake

Parking brake (electromechanical parking brake = EMF)
As series standard, the E70 is equipped with an electromechanical parking brake (EMF). The parking brake is the same as a handbrake. The parking brake is familiar from the BMW 7 Series. The parking brake is operated using the parking brake button in the centre console.
The configuration of the parking brake meets the following requirements:
- exclusion of all states where safety is critical
- optimal functionality
- greatest availability
- best convenience

The parking brake serves to secure the stationary vehicle against rolling away. When the engine is off, the EMF engages the parking brake: electromechanically via the actuating unit. With the engine running, the dynamic stability control (DSC) engages the parking brake: hydraulically via the 4 wheel brakes.
New from 10/2007: The automatic hold function is also available. The automatic hold function is activated using a button behind the parking brake button. The button is connected to the Dynamic Stability Control (DSC). Once the function has been selected, the vehicle is held in place hydraulically by the DSC after braking to a standstill.
Pressing the accelerator pedal releases the wheel brakes and the vehicle begins to move. The automated braking and release process supports driving in city traffic or in jams, for example.

Brief component description
The following components are described for the parking brake:

Actuating unit and EMF control unit







The actuator unit is attached to the rear-axle member.
The actuator unit is parking brake is sealed and water-tight. The housing cannot be opened in service.
The actuator unit consists of:
- EMF control unit
- Electric motor
- Transmission
- Force sensor







The rear distribution box supplies the EMF with voltage (terminal 30 twice).
The Bowden cables are adjusted electromechanically via the electric motor with flanged-on gearing. Here, each of the Bowden cables act on a brake shoe expander that sets the drum brake on the rear wheel.
The force sensor delivers the EMF control unit the actuating force. Recording the actuating force is necessary to ensure the required brake force.A spring is integrated in the force sensor, in which the Bowden cables end. The force sensor measures the travel when the springs are compressed. The travel measurement is based on the Hall effect.

Parking brake button
The parking brake button is located in the centre console behind the gear selector switch (GWS). The design of the parking brake button is based on the operations logic of a handbrake:
- Pull parking brake button upwards: the parking brake is activated
- Pull parking brake button downwards: the parking brake is deactivated







An indicator lamp in the instrument cluster shows that the parking brake has been activated.
The following additional control units are involved in the electromechanical parking brake (EMF):

DSC: Dynamic stability control
The dynamic stability control (DSC) is the master control unit for the electromechanical parking brake (EMF). With the engine running, the dynamic stability control (DSC) engages the parking brake. The DSC also delivers the conditioned wheel speed (front left) from the active wheel speed sensor. The signal is transferred across a separate line. The signal is particularly important for detection of the vehicle standstill.
In addition, the DSC sends the driving speed as a plausibility check (averaged over the 4 wheel speed sensors) on the PT-CAN. In addition to the plausibility check, the gearbox output speed of the automatic gearbox is used.







Via DSC, dynamic emergency braking can also be initiated with the parking brake button.

DME or DDE: Digital Motor Electronics or Digital Diesel Electronics
The engine management system delivers the signal "Engine running". The signal is transferred across the PT-CAN.

EGS: electric gearbox control
The electric gearbox control delivers the following signals:
- Selector lever position (e.g. D): this detects driving off against the parking brake (Check Control message).
- Gearbox output speed:plausibility check of the speed signal.

KOMBI: Instrument panel control unit
In the event of failure of or a fault in the EMF, the warning and indicator lamp for the EMF lights up. In addition, a Check Control symbol is displayed in the LC display.







If there is a Check Control message, additional supplementary instructions can be displayed on the Central Information Display (CID).

JBE: Junction Box electronics
The junction box electronics (JBE) form the gateway between the PT-CAN and K-CAN.

System functions
The following system functions are described for the parking brake:
- Engaging and disengaging
- Dynamic emergency braking
- Roll monitoring
- Safeguard at a standstill
- Emergency release of the parking brake
- Braking-in after maintenance measure

Engaging and disengaging
The brake is engaged by pulling the parking brake button. With the engine running or rolling vehicle: via the DSC, the handbrake is applied hydraulically on the disc brakes of the front and rear axles. With the engine off and the vehicle stationary: the parking brake is applied with the help of the electromechanical actuating unit via Bowden cables to the drum brakes of the rear axle.
Driving off against the blocked brake pressure leads to another pressure increase and a Check Control message. Starting the engine leads to a switch from electromechanical to hydraulic parking brake engagement.
The parking brake is disengaged by pressing the parking brake button. The active brake system opens. When the vehicle is stationary and the engine is running or off, it is only possible to disengage the parking brake with the brake pedal operated.
With the engine off (via bus signal "status engine running"), there is a switch from hydraulic to electromechanical engagement of the parking brake.

Dynamic emergency braking
If the parking brake button is pulled while the vehicle is being driven, hydraulic braking occurs for 0.8 s with 3 m/s2 . For the next 2 seconds, the braking power is increased (linear) to 5 m/s2 . As long as the vehicle is rolling and the engine is running, emergency braking is handled by the hydraulic components. With the engine off and the vehicle stationary, emergency braking is handled by the mechanical system. The braking is maintained by the DSC for as long as the parking brake button is pulled. Here, all DSC control operations are run as if via the brake pedal. As the dynamic emergency braking acts hydraulically on all 4 wheels, significantly greater decelerations with a minimum of actuating force are possible compared to conventional parking brakes. For safety reasons, the following traffic is warned by the brake lights in the event of dynamic emergency braking. Dynamic emergency braking via the handbrake is intended for emergencies and under no circumstances does it replace braking with the brake pedal.
If braking by the brake pedal and parking brake overlap, the DSC decides on the higher specified value. On emergency braking to vehicle standstill, the vehicle remains hydraulically braked even after the parking brake button is released. It is only when the parking brake button is pressed again that the hydraulic brake is released.

Roll monitoring
Roll monitoring prevents the vehicle with engaged parking brake from rolling away. The roll monitoring observes the wheel speed signals of the braked wheels after the parking brake has been applied. The wheel speed signal indicates that the vehicle is rolling away. If rolling away is reliably determined, the activated brake system retensions the brakes.
The roll monitoring is disabled on:
- Disengaging the parking brake
- Sleeping of the vehicle

Safeguard at a standstill
This function activates the mechanical brake application if the vehicle has to be additionally safeguarded when the hydraulic brake has been applied (e.g. driver leaves the vehicle). The DSC control unit detects when the driver leaves the hydraulically braked vehicle (CAN message, e.g. via seat occupancy detection). The DSC then requests the EMF to add mechanical brake application. The EMF releases the additional braking when signals arrive that indicate the driver has returned.

Emergency release of the parking brake
In the event of failure of the EMF (e.g. fault entry) or inadequate voltage supply, a mechanical emergency release is implemented. The emergency release mechanism enables manual release of the actuating unit.

IMPORTANT: Secure against rolling away.

Before operating the emergency release, secure the vehicle against rolling away.
Emergency release is performed manually by means of a Bowden cable and a handle from the on-board tool kit.
The actuator for the drum brake is released in the actuating unit.







After emergency release of the parking brake, it might be that the vehicle still cannot be moved after an interruption to the voltage supply. The parking lock of the automatic gearbox might still be engaged. When the parking brake has been emergency-released: apply strong pressure to the brake. After ignition ON, press the parking brake button downwards once. The emergency release is locked. The parking brake closes automatically. This runs a detection of a cable break via the force sensor. Subsequently, the parking brake opens automatically.

Notes for Service department

General Information

IMPORTANT: Replace the brake shoes of the parking brake.

Bedding-in is required after replacing the brake pads on the drum brake. For this, a service function is available in the BMW diagnosis system.

Diagnosis instructions
The following service functions are available in the BMW diagnosis system:
- Run the braking-in program
Bedding-in is required after replacing the brake pads on the drum brake.
- Workshop mode
Before replacement of the parking brake, the service function 'Workshop mode' must be run. In the service function, select 'Set workshop mode'. The parking brake is moved into the opened position and temporarily disabled. Subsequently, the parking brake can be replaced.
A new parking brake is delivered in the workshop mode. After installation, the service function must be run. In the service function, select 'Delete workshop mode' (or drive faster than 3 km/h).
- Initial operation
After replacement of the parking brake, it must be commissioned.
During this commissioning, a function test is carried out. Procedure:
- Ignition ON
- Apply strong pressure to the brake pedal
- Hold the brake pedal pressed down
- Pull the parking brake button (engage)
- Push the parking brake button (disengage)

NOTE: The sound on engaging the actuating unit is very quiet.

If engaging and disengaging the parking brake were detected, the fault memory of the EMF must be deleted subsequently.

NOTE: Fault entry in the DSC.

After replacement of the parking brake, the DSC has a fault entry (interface).

Notes on encoding/programming

After replacement of the actuating unit, the EMF control unit must be coded.

National-market version
The indicator lamps in the instrument cluster as well as the Check Control symbols are designed as country specific.
No liability can be accepted for printing or other errors. Subject to changes of a technical nature