Principles of Operation
PRINCIPLES OF OPERATIONStatic Apply
The parking brake control module receives a vehicle speed signal from the ABS module on the high speed CAN bus. If the parking brake switch is pulled to the 'Apply' position and vehicle speed is less than 2 mph (3 km/h), the control module will instigate its 'Static Apply' mode and drive the actuator to apply full parking brake force to the rear wheels.
The parking brake control module monitors the current drawn by the actuator and compares this to information held within its configuration software to determine when full braking force has been applied.
Dynamic Apply
There are 2 'Dynamic Apply' modes; low speed dynamic and high speed dynamic. The low speed dynamic mode operates at speeds between 2 mph (3 kph) and 20 mph (32 kph). The high speed dynamic mode operates at speeds above 20 mph (32 kph)
If the parking brake switch is pulled up to the 'Apply' position and vehicle speed is within the low speed dynamic range, the control module drives the actuator to apply full parking brake force to the rear wheels.
If the parking brake switch is pulled up to the 'Apply' position and vehicle speed is within the high speed dynamic range, the control module will apply braking force to the rear wheels at a slower rate until full braking load is reached or the switch is released. The rate with which braking force is applied is controlled by the control module, which monitors both current drawn by the actuator and positional information from the actuator hall sensor and compares this to information held within its configuration software.
Drive Away Release
The parking brake control module will initiate its 'Drive Away Release' function and automatically release the parking brake if the following conditions are detected:
^ The engine is running
^ Drive (D), or Reverse (R) is selected
^ Positive throttle movement is detected
The control module receives messages of gear selector lever position and throttle angle over the high speed CAN bus from the gear selector module and the Engine Control Module (ECM) respectively.
Release from Park
The parking brake control module will initiate its 'Release from Park' function and automatically release the parking brake if the gear selector lever is moved from Park (P) to any position except Neutral (N).
NOTE: A 'between gears' positioning of the gear selector level will not initiate 'Release from Park'.
Repairs
Before carrying out any work on the parking brake system, the Integrated Diagnostic System (IDS) must be connected and the 'parking brake unjam' routine run. The routine can be found in the 'Vehicle Configuration' area, under the 'Set-up and Configuration' menu. After any work has been carried out on the parking brake, the system will require resetting.
CAUTION: Do not use the 'Emergency Release' tool to allow work to be carried out on the parking brake. Work can only be carried out on the parking brake system after the 'parking brake unjam' routine has been run.
Resetting
If the electrical supply is disconnected from the parking brake control module, the actuator will loose its position memory. On battery reconnection and ignition on, 'APPLY FOOT AND PARK BRAKE' will be displayed in the instrument cluster message center indicating the parking brake requires resetting. To reset the parking brake, press and hold the foot brake. While holding the foot brake in position, move the parking brake switch to the 'Apply' position.
Operating Voltages
The control module will only operate the actuator if the power supply from the battery is between 9 V and 16 V. At any voltage within this range, the actuator is able to fully tighten and release the brake cables. If the power supply falls outside of the range, a fault code is stored in the parking brake control module and can be retrieved using IDS.