LR3/Disco 3
To reduce quiescent drain on the vehicle battery, the parking brake module incorporates a sleep mode. The parking brake
module enters the sleep mode, provided the ignition is off and there are no signals from the wheel speed sensors, when
one of the following occurs:
l
20 minutes elapse after the last actuation of the parking brake.
l
If no actuation occurred, 20 minutes elapse after the ignition is switched off.
The parking brake module wakes up from the sleep mode when on of the following occurs:
l
An apply or release request is made with the parking brake switch.
l
The ignition is turned on.
l
A key out apply is activated.
The parking brake module wakes up within 500 ms. The high speed CAN bus is activated within 200 ms maximum.
When the parking brake module is woken with a release request from the parking brake switch, the parking brake module
ignores the request but illuminates the red brake warning indicator. The parking brake module extinguishes the red brake
warning indicator and goes back to sleep immediately the switch is released to the neutral position.
When the parking brake module is woken with an apply request from the parking brake switch, if the parking brake is
already applied the parking brake module ignores the request but illuminates the red brake warning indicator. The parking
brake module extinguishes the red brake warning indicator and goes back to sleep immediately the switch is released to
the neutral position. If the parking brake is in the released condition when the apply request is made, the parking brake
module illuminates the red brake warning indicator and applies the parking brake. The parking brake module extinguishes
the red brake warning indicator and goes back to sleep 3 minutes after the apply activation, or immediately after the
switch is released to the neutral position, whichever occurs last.
Dynamic Apply
In the dynamic apply mode, if the vehicle speed is more than 10 km/h (6.25 mph) when the parking brake switch is
selected to apply, the parking brake module requests the ABS module to activate the disc brakes on all four wheels.
When the vehicle comes to a standstill, the parking brake module statically applies the parking brake. Once the static load
is achieved, the hydraulic pressure is removed. If the parking brake switch is released to the neutral position, or pressed
down to the release position, during dynamic apply, braking is cancelled.
The ABS module monitors the deceleration rate using the wheel speed sensor signals, and adjusts the hydraulic pressure
to the disc brakes as required to achieve the required rate. All of the anti-lock control - traction control system brake
functions remain enabled in the dynamic apply mode.
The parking brake module incorporates two fallback functions for the dynamic apply mode.
l
Fallback 1 is invoked if vehicle speed is between 2.5 km/h (1.25 mph) and V when the parking brake switch is
selected to apply and the ABS module is unable to fulfil a hydraulic request. When fallback 1 is invoked, the
parking brake module decelerates the vehicle, using only the parking brake. The parking brake module monitors
the deceleration rate using the wheel speed information from the ABS module, and adjusts the tension of the
brake cables to achieve the required rate. During deceleration the parking brake module also uses the wheel
speed inputs from the ABS module to operate an anti-lock function for the rear wheels. When vehicle speed
decreases to 2.5 km/h (1.25 mph) the parking brake module static applies the parking brake.
l
Fallback 2 is invoked if there is a loss of communication between the parking brake module and the ABS module
or the CAN bus has failed. When fallback 2 is invoked, the parking brake module decelerates the vehicle using
only the parking brake. The parking brake module tightens the brake cables under the control of the driver, no
anti-lock function is available.
While dynamic apply is active, including fallback 1 and fallback 2, the parking brake module also outputs high speed CAN
bus signals to:
l
The ABS module, to apply the stoplamps.
l
The instrument cluster, to sound an intermittent warning buzzer, at 0.5 second on, 1.0 second off.
l
The instrument cluster, to illuminate the red parking brake warning indicator. The indicator is permanently
illuminated except in fallback 2, when it flashes.
DAR Pre-arming
