FREE REPAIR MANUALS & LABOR GUIDES 1982-2013 Vehicles
Courtesy of Operation CHARM: Car repair manuals for everyone.
Home >> Volvo >> 2009 >> XC70 AWD L6-3.0L Turbo VIN 99 B6304T2 >> 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 3 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 transmitted 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
- start switch (start button) must have been activated or the engine must be running. Information about this is retrieved from the central electronic module (CEM) (4/56) via the CAN network.
- signal from the clutch pedal sensor alternatively brake pedal sensor. The engine control module (ECM) (4/46) supplies information about the clutch pedal position. Engine control module (ECM) supplies information about the position of the brake pedal (applies to vehicles with manual transmission).
- signal from the brake pedal sensor. Brake control module (BCM) (4/16) supplies information about the position of the brake pedal (applies to vehicles with automatic transmission).
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.

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 clutch pedal position (only manual transmission), from the engine control module (ECM) and central electronic module (CEM) (4/56) via the CAN network
- the gas pedal position from the Engine Control Module (ECM) via the Controller Area Network (CAN).
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 the parking brake switch (3/272) is activated for the duration. The ABS function is used to prevent overloading the parking brake and to quickly reduce the speed. In order for activation of the parking brake while moving to be possible, the function of automatic deactivation when stationary must have been used.
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 until the system's max. limit is reached. 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 steps until the system's max. limit is reached.

pro multis Credits:Operation CHARM About Operation CHARM