Operating modes
Mode | Prerequisites | Driver action |
Static inclusion | Vehicle speed is less than 2.5 km/h. | Pull the parking brake switch up. |
Static Shutdown | 1, Vehicle speed less than 2.5km/h. 2, The engine is running. OR Ignition key in position II and brake or clutch pedal depressed (for models with manual transmission). OR Ignition key in position II and accelerator pedal or clutch pedal depressed (for models with automatic transmission). | Push the parking brake switch down. |
Power on when key is removed (only for models with manual transmission) | 1, Vehicle speed less than 10km/h. 2, Key in ignition position 0. 3, Key in ignition. | Remove the key from the ignition lock. |
Prohibition of switching on when removing the key | 1, Vehicle speed less than 2.5km/h. 2, Key in ignition position 0. 3, Key in ignition. | Remove the key from the ignition while holding down the parking brake switch. |
Dynamic enable | Vehicle speed over 2.5 km/h. | Pull the parking brake switch up as required. |
Dynamic Shutdown | Vehicle speed over 2.5 km/h. | Turn off (move to neutral) or push down the parking brake switch. |
DAR (automatic shutdown when driving) (only for models with automatic transmission) | 1, Ignition key in position II. 2, Gear selector in position 1, 2 or R (at the selected higher level) or 1, 2, 3 or R (at the selected lower stage). 3, Accelerator pedal depressed more than 5%. | Absent. The parking brake is automatically released when you start driving. |
Working voltage
Actuation (turn on or off) parking brake control is only possible when the parking brake control unit supply voltage is in the range of 9-18 V. At any voltage in this range, the parking brake control unit can provide maximum tension to the brake cables, fully applying the parking brake. However, in the range of 9-10.5 V, the actuation time may exceed 1 second.
While applying the parking brake:
- If the parking brake control module supply voltage drops below 8.3 V, the parking brake control module continues to perform the operation, but stores the corresponding DTC. When the ignition is on, the parking brake control module also sends signals to the instrument panel to turn on the yellow parking brake indicator and flash the red parking brake indicator. For vehicles with a high-level instrument cluster, the message center display shows a parking brake fault message. Warnings are cleared when the supply voltage exceeds 8.3V.
- If the supply voltage drops below 7.5 V, the parking brake control unit stops the operation. The operation resumes automatically when the supply voltage exceeds 7.5 V and the command from the parking brake switch is still being received.
- If the supply voltage drops below 6.5 V, the parking brake function is disabled before the end of the ignition cycle.
- If the supply voltage exceeds 18.0 V, the parking brake control unit immediately disables the parking brake function and stores the corresponding fault code. When the ignition is on, the parking brake control module also sends signals to the instrument panel to turn on the yellow parking brake indicator and flash the red parking brake indicator. For vehicles with a high-level instrument cluster, the message center display shows a message that the parking brake is defective and does not work. The parking brake function is disabled until the supply voltage is back in the 9-18V range. When the supply voltage is back in the 9-18V range, the warning will stop and the operation will automatically resume if the parking brake control unit is in dynamic mode at active request from the parking brake switch.
NOTE: Below 8 volts the instrument panel will turn off, so below 8 volts the indicators will not work and no warnings will be given. CAN communication stops when the battery voltage is below 7.0V and resumes when the voltage is above 7.5V.
Standby mode
To reduce battery discharge at rest, the parking brake control unit has a standby mode. The parking brake control module enters standby mode with the ignition off and no signals from the wheel speed sensors when one of the following conditions is met:
- It has been 20 minutes since the parking brake was last applied.
- If the parking brake has not been applied, 20 minutes have passed since the ignition was turned off.
The parking brake control module wakes up when one of the following conditions is met:
- The parking brake switch has received a request to engage or disengage.
- Ignition on.
- Turned on when key was removed.
The parking brake control unit wakes up in 500 ms. High speed CAN bus (controller network) turns on in no more than 200 ms.
If the parking brake control module wakes up on a release request from the parking brake switch, the parking brake control module ignores this request and turns on the red brake light. The parking brake control module turns off the red brake indicator and returns to standby mode immediately after the switch is moved to the neutral position.
If the parking brake control module wakes up on an application request from the parking brake switch and the parking brake control module is already on, the parking brake control module ignores the request and turns on the red brake light. The parking brake control module turns off the red brake indicator and returns to standby mode immediately after the switch is moved to the neutral position. If the parking brake is released when an application request is made, the parking brake control unit turns on the red brake indicator and the parking brake. The parking brake control module turns off the red brake indicator and returns to standby mode 3 minutes after it is turned on, or immediately after the switch is moved to the neutral position, whichever event occurred last.
Dynamic enable
In dynamic enable mode, the system operates as follows. When the speed exceeds 10 km/h, provided that the parking brake switch is in the on position, the parking brake control module sends a request to the ABS module to apply the disc brakes on all four wheels. When the vehicle comes to a complete stop, the parking brake control unit applies the parking brake statically. When the static load is reached, the hydraulic pressure is released. If the parking brake switch is released to the neutral position or pushed down to the off position during dynamic engagement, braking stops.
ABS module (anti-lock system) controls deceleration from wheel speed sensors and adjusts hydraulic pressure on the brake discs to achieve the desired deceleration. When operating in dynamic engagement mode, all functions of the anti-lock braking and traction control systems are active.
The parking brake control unit has two fallback functions for dynamic engagement.
- Fallback function 1 is activated when the speed is between 2.5 km/h and V, the parking brake switch is in the on position, and the ABS module (anti-lock system) cannot generate the required hydraulic pressure. When fallback function 1 is activated, the parking brake control unit brakes the vehicle using only the parking brake. The parking brake control module controls deceleration based on wheel speed information from the ABS module (anti-lock system) and adjusts the tension of the brake cables to achieve the desired deceleration. Also during deceleration, the parking brake control unit uses the wheel speed signals from the ABS module (anti-lock system) to control the anti-lock function of the rear wheels. When the vehicle speed drops to 2.5 km/h, the parking brake control unit switches to static mode.
- Fallback function 2 is activated when there is no communication between the parking brake control unit and the ABS module (anti-lock system) , or CAN bus malfunction (controller network) . When fallback function 2 is activated, the parking brake control unit brakes the vehicle using only the parking brake. The parking brake control module tightens the brake cables under the control of the driver, and the anti-lock function is not available.
When the brake is applied dynamically, including fallback functions 1 and 2, the parking brake control unit also transmits on the high speed CAN bus (controller network) signals to the following devices:
- ABS module (anti-lock system) to turn on the stop lights.
- Instrument panel to activate the intermittent warning signal (active signal 0.5 s, pause 1.0 s).
- Instrument panel to turn on the red parking brake indicator. The indicator lights up constantly, except for the activation of the fault function 2, when it flashes.
DAR pre-training
Preliminary preparation of DAR is carried out when the top stage of the transfer case is engaged, and serves to reduce the time for disengaging the parking brake during smooth starting using the DAR function. DAR preconditioning is performed in the following situation:
- The ignition switch is in position II.
- The gearbox operates in mode 1, 2 or R.
- The car is stationary.
- Cables are not tensioned in emergency mode.
Automatic load regulation
When the ignition is on, the parking brake control unit constantly monitors the signal from the force sensor. If the tension of the brake cables is outside the limits set for the current mode, the parking brake control unit automatically returns the tension to the allowable range.
Emergency tension. If the vehicle is moving during preconditioning, the maximum cable tension is set until the end of the current ignition cycle.
Auto power on. If, when the parking brake is applied, the tension of the brake cables decreases by a predetermined amount relative to the initial setting, the parking brake control unit automatically restores the tension corresponding to the initial setting.
Automatic shutdown. If the brake cable tension increases by a predetermined amount when the parking brake is released, the parking brake control unit automatically reduces the tension to zero.
Parking brake switch control
The parking brake control module monitors the parking brake switch system for the following faults. When a malfunction is detected, the parking brake control unit stores the appropriate fault code:
- Short circuits between the matching transistor in the parking brake control module and the battery voltage circuit.
- Breaks in wires and malfunctions of microswitches.
- Reliability.
The parking brake switch is internally redundant. If one microswitch malfunction is detected, the parking brake control unit can still determine the state of the parking brake switch. As a result of short circuits or several faults, the parking brake control module will deactivate the parking brake switch until the end of the current ignition cycle. In addition, the parking brake control unit disables the parking brake switch when a plausibility check error is detected. However, since plausibility check errors are typically caused by incomplete actuation of the parking brake switch, the switch will re-operate if the parking brake control unit subsequently determines that the switch is in a valid operating state.
If one microswitch malfunction is detected, the parking brake control unit sends a signal to the instrument panel to turn on the yellow parking brake indicator. On vehicles with a high-level instrument panel, the parking brake control module also commands the instrument panel to display a parking brake fault message. During application, the parking brake control module also sends a request to the instrument panel to flash the red parking brake indicator.
For all other faults, the parking brake control unit sends a signal to the instrument panel to turn on the yellow parking brake indicator and, for vehicles with a high-level instrument panel, a command to display a message that the parking brake is faulty and does not work. If applied, the parking brake control module sends a flashing red parking brake indicator signal to the instrument panel until the end of the current ignition cycle.
On the next ignition cycle, the lights will turn on and messages will only come on if the fault is still present, although the parking brake control module will store the fault code until it is cleared with T4.
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