# Electric Park Brake

## Overview

### Component Location

1. RH rear brake rotor

2. RH rear park brake caliper

3. ECU

4. LH rear park brake caliper

5. LH rear brake rotor

6. Park brake button

### General

The Electro-mechanical Park Brake (EPB) system operates on the rear wheels only. The vehicle uses one electrically operated sliding-type park brake caliper on each rear wheel. Each caliper uses a single piston, operated by an electric motor, through a mechanical gear reduction. The piston is applied and released electrically, but is held in the applied position mechanically. The EPB system is driven by a dedicated Electronic Control Unit (ECU) located in the trunk on the passenger’s side, behind the rear wheel.

The EPB is operated either by using the touchscreen or by pressing the P button on the selector stalk. The EPB is automatically applied when the vehicle is shifted to P, or when the vehicle speed is below the threshold and the driver is leaving the vehicle.

Activation of the system applies the EPB calipers to stop the vehicle moving and enables parking of a fully loaded vehicle on a 20% grade.

The EPB has two modes of operation:

- Static mode (see Static Mode)

- Dynamic mode (see Dynamic Mode)

## Component Descriptions

### ECU

1. EPB Electronic Control Unit (ECU)

The ECU comprises two individual controllers that simultaneously monitor the calipers. If one controller fails or there is a mismatch between the two, a fault is triggered. With respect to firmware, the controllers are identified as EPB and EPBM.

The ECU is pre-programmed with operating parameters for the EPB, and determines the clamping force applied to the calipers using signals received from the driver and CAN data signals from other vehicle management systems.

Diagnostic Trouble Codes (DTCs) and live data parameters can be accessed using Toolbox.

The ECU receives CAN signals from the P button on the gear selector stalk and the Park Brake icon on the touchscreen. These CAN signals are used in conjunction with CAN signals from other systems to apply and release the EPB. The calipers receive a 12 Volt supply from the ECU through 20 Amp fuses that are located in the underhood fuse box. The ECU uses a target current level to clamp the calipers to the rotors. This ensures that the correct clamping loads are used for the prevailing conditions.

### Parking Brake Caliper

1. Caliper body

2. Caliper securing bolts (x2)

3. Caliper motor

4. Brake pads

5. Brake pad retaining pin (x2)

6. Anti-rattle pin

The parking brake calipers are operated by electric motor. When the parking brake is applied, the motor, which is inboard of the rotor, pushes the inboard pad against the rotor. This causes the caliper body to slide inward on the guide pins, pressing the outboard pad against the rotor.

The clamping force is increased with increased ambient temperature and hill gradient. Hall effect sensors within the calipers provide feedback on piston position to the ECU. If a fault occurs in the EPB system, the red EPB indicator light displays in the instrument panel and on the touchscreen.

To release the EPB, the ECU reverses the polarity of the caliper motors.

Toolbox has a function that allows the EPB caliper piston to be automatically retracted for servicing.

### EPB Indicator Light

The EPB indicator light displays when the EPB is applied. It also displays if a fault is detected. In addition to the indicator light, some faults might trigger a chime and a warning message.

## Operation

### Static Mode

The parking brake can be applied and released using two separate controls.

1. The P button on the gear selector stalk:

   - The EPB system automatically engages when the vehicle is stationary and the selector lever is in Park. The PRND indicator displays P. The EPB calipers are applied and remain applied.

   - The EPB system automatically disengages when the gear selector is shifted from Park to Drive, Reverse, or Neutral, displaying D, R, or N in the dash panel.

2. The Park Brake icon on the touchscreen:

   - The EPB is applied when the vehicle is stationary and the gear selector is in Drive, Neutral, or Reverse by selecting the Park Brake icon on the touchscreen. The PRND indicator displays N.

   - The EPB is released by selecting the Park Brake icon on the touchscreen. The PRND indicator displays N.

### Dynamic Mode

The dynamic park brake mode is designed to slow a moving vehicle in the unlikely event of a hydraulic brake system failure. Dynamic park brake mode applies the EPB calipers to slow the vehicle at a moderate rate.

To activate the dynamic mode, press and hold the P button on the gear selector stalk or the Park Brake icon on the touchscreen. The brake releases when the icon or control button is released.

If the vehicle is brought to a complete standstill using dynamic mode, the EPB adopts static mode and remains engaged. To disengage the EPB system, use either the gear selector stalk or touchscreen icon as described in Static Mode, page 3-7.

### EPB Failure Modes

If the EPB fails to operate, the above message appears on the instrument cluster and on the touchscreen advising the driver of the situation.

If the EPB fails to engage, chock the wheels to prevent the car from rolling away.

If the EPB fails to release, do not attempt to drive the car until the fault is repaired.