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Home >> Volvo >> 2012 >> S60 R Design AWD L6-3.0L Turbo VIN 90 B6304T4 >> Repair and Diagnosis >> Brakes and Traction Control >> Parking Brake System >> Description and Operation >> Function

Function






Function

Activating/deactivating the parking brake in stationary vehicles




Vehicles are defined as stationary up to a speed of 7 km/h.
It is always possible to activate the parking brake. When the driver presses the parking brake switch (3/272) an analog signal is sent to the parking brake module (PBM) (4/115) which activates the electric motor in the brake caliper (6/146-147), which in turn presses on the brake pads.
To deactivate (release) the parking brake the park brake module (PBM) requires information about the following:
- signal from the parking brake switch
- key in ignition, or the engine must be running. Information about this is retrieved from Central electronic module (CEM) (4/56) via CAN-net
- signal from brake pedal position sensor or clutch pedal sensor. Central electronic module (CEM) (4/56) supplies information about the brake pedal's position (applies for key in accessory position)
- signal from brake pedal position sensor. Brake control module (BCM) (4/16) supplies information about the brake pedal's position (applies with ignition on, engine running, or at start attempt).
The Park Brake Module (PBM) retrieves information from the above control modules by reading messages on the CAN network.
If all conditions are met the Park Brake Module (PBM) activates the electric motor in the brake caliper and releases the brake pads.
The parking brake can also be activated automatically upon request by Forward Sensing Module (FSM) (Applies to vehicles equipped with Forward Sensing Module (FSM)).
See: Design and Function - Forward Sensing Module (FSM).

Automatic deactivation of the parking brakes




This means that the parking brake is automatically released when the driver drives off. A condition for this is that the parking brake was activated when the car was stationary. The following information about the vehicle is required for the park brake module (PBM) (4/115) to release the parking brake at the right moment:
- current gear (only automatic transmission), from transmission control module (TCM) (4/28) via the CAN network
- the engine torque, from Engine Control Module (ECM) (4/46) via the Controller Area Network (CAN)
- the vehicle angle, from the vehicle angle sensor in the Park Brake Module (PBM)
- the gas pedal's position from the Engine Control Module (ECM) via the Controller Area Network (CAN)
- driver buckled up, (only automatic transmission), from Supplemental restraint system module (SRS) (4/9) via CAN-net.
Park Brake Module (PBM) uses the information above to calculate when the engine torque is sufficient for the vehicle to be stationary when the parking brake is released.

Activating/deactivating the parking brake when moving
It is possible to activate the parking brake while moving, that is to say at speeds exceeding 3 km/h. But this is an emergency function which must only be used when the normal brakes are not functioning.
A condition is that switch parking brake (3/272) is activated during the whole sequence. The ABS-function is used to obtain safe braking.
A sound signal is heard when the parking brake is activated when driving.
When activating the parking brake when moving the Park Brake Module (PBM) (4/115) will transmit a request, to the brake control module (BCM) (4/16) via the CAN network, to brake the vehicle using the ABS function. When the speed is less than 3 km/h the park brake module (PBM) will take over the braking by activating the electric motor in the brake calipers (6/146-147).

Rolling brake test
Park Brake Module (PBM) has a function for rolling brake test. Rolling brake test is used to check the function of the electrically operated parking brake, e.g., during the annual vehicle inspection.
The following conditions must be fulfilled for 3 seconds before the test and remain during the test for Park Brake Module (PBM) to allow rolling brake test:
- Speed front wheel: 0 km/h.
- Speed rear wheel: 2 - 8 km/h.
- Ignition on/engine running.
- No trouble codes related to switch parking brake, electric motor in brake calipers, or speed signal from Brake control module (BCM).
Remarks
If conditions for rolling brake test are not met when switch parking brake is activated, then Park Brake Module (PBM) will perform normal application of the parking brake.

There are two different ways to activate rolling brake test:
- Activate (hold in) switch parking brake. When switch parking brake is activated then Park Brake Module (PBM) will activate the electric motor in the brake calipers (6/146-147), which presses on the brake pads until minimum required brake force is reached. Then the brake force increases automatically every third second in four steps. Increase of the brake force occurs in steps for a total of approx. 10 seconds.
- Activate (press in) switch parking brake repeatedly. Activate (press in) switch parking brake once. When switch parking brake is activated then Park Brake Module (PBM) will activate the electric motor in the brake calipers (6/146-147), which presses on the brake pads until minimum required brake force is reached. At repeated activation of switch parking brake, the brake force increases in four steps.

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