Sleep Mode
To reduce quiescent drain on the vehicle battery, the EPBCM incorporates a sleep mode. The EPBCM 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:
- minutes elapse after the last actuation of the parking brake.
- If no actuation occurred, 20 minutes elapse after the ignition is switched off.
The EPBCM wakes up from the sleep mode when on of the following occurs:
- An apply or release request is made with the parking brake switch.
- The ignition is switched on.
- A key out apply is activated.
The EPBCM wakes up within 500 ms. The HS CAN bus is activated within 200 ms maximum.
When the EPBCM is woken with a release request from the EPB switch, the EPBCM ignores the request but illuminates the red brake warning indicator. The EPBCM extinguishes the red brake warning indicator and goes back to sleep immediately the switch is released to the neutral position.
When the EPBCM is woken with an apply request from the EPB switch, if the parking brake is already applied the EPBCM ignores the request but illuminates the red brake warning indicator. The EPBCM 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 EPBCM illuminates the red brake warning indicator and applies the parking brake. The EPBCM 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 EPB switch is selected to apply, the EPBCM requests the Anti-lock Brake System (ABS) control module to activate the disc brakes on all four wheels. When the vehicle comes to a standstill, the EPBCM statically applies the parking brake. Once the static load is achieved, the hydraulic pressure is removed. If the EPB switch is released to the neutral position, or pressed down to the release position, during dynamic apply, braking is cancelled.
The ABS control 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 antilock control - traction control system brake functions remain enabled in the dynamic apply mode.
The EPBCM incorporates two fallback functions for the dynamic apply mode.
- Fallback 1 is invoked if vehicle speed is between 2.5 km/h (1.25 mph) and Vmax when the EPB switch is selected to apply and the ABS control module is unable to fulfill a hydraulic request. When fallback 1 is invoked, the EPBCM decelerates the vehicle, using only the parking brake. The EPBCM monitors the deceleration rate using the wheel speed information from the ABS control module, and adjusts the tension of the brake cables to achieve the required rate. During deceleration the EPBCM also uses the wheel speed inputs from the ABS control module to operate an anti-lock function for the rear wheels. When vehicle speed decreases to 2.5 km/h (1.25 mph) the EPBCM switches to the static apply mode.
- Fallback 2 is invoked if there is a loss of communication between the EPBCM and the ABS control module or the CAN bus has failed. When fallback 2 is invoked, the EPBCM decelerates the vehicle using only the parking brake. The EPBCM 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 EPBCM also outputs HS CAN bus signals to:
- The ABS control module, to apply the stoplamps.
- The IC, to sound an intermittent warning buzzer, at 0.5 second on, 1.0 second off.
- The IC, to illuminate the red parking brake warning indicator. The indicator is permanently illuminated except in fallback 2, when it flashes.