Anti-Lock Brake System (ABS) and Stability Control - System Operation and Component Description

conditions have been met, the hill start assist feature automatically engages. As the driver releases the brake pedal, the ABS module commands the HCU to close the isolation valves which maintain the current brake system pressure, preventing the vehicle from rolling down the incline. Once the driver presses the accelerator pedal and the torque produced by the engine reaches a specific level, the ABS module gradually releases the brake pressure to make sure the vehicle is neither rolling back nor driving off until there is sufficient driving torque to move the vehicle forward (or backward if reversing up the incline). For vehicles with an automatic transmission the incline must be greater than 3.5 degrees (approximately a 6% grade), for vehicles with a manual transmission the incline must be greater than 1.5 degrees (approximately a 3% grade). On vehicles with a manual transmission the hill start assist feature can be disabled through the message center. On vehicles with an automatic transmission the hill start assist feature cannot be disabled by the driver.

Supplemental Braking Assist

The ABS module uses the HCU and hydraulic pump motor to help bring the vehicle to a safe, controlled stop in the event of severe vacuum loss in the brake booster. The ABS module continually monitors the vacuum in the brake booster through the use of a vacuum sensor. When the vacuum sensor indicates vacuum is below a predetermined level, a DTC is set in the ABS module. The ABS module sends a message to the GWM over the HS-CAN2 to illuminate the red brake warning indicator, the GWM relays this message to the IPC over the HS-CAN3. If a low vacuum condition occurs during a braking event or if the driver attempts to stop the vehicle with a low vacuum condition in the brake booster, the ABS module activates the hydraulic pump motor in the HCU to assist with vehicle braking.

On vehicles equipped with adaptive cruise control, the CCM monitors the area forward of the vehicle. When an object enters this area and closes the distance gap set by the driver, the CCM sends either an adaptive cruise control deceleration request or a collision avoidance deceleration request to the ABS module over the HS-CAN2. When the deceleration request message is received, the ABS module activates the hydraulic pump motor and solenoid valves in the HCU to slow the vehicle down to maintain the distance gap set by the driver. Once the distance gap set by the driver is achieved, the CCM stops sending the deceleration request message and the ABS module deactivates the hydraulic pump motor and solenoid valves in the HCU. If the CCM determines the amount of braking provided by the ABS module is insufficient, the CCM sends a forward collision avoidance braking request message to the ABS module and warns the driver, both audibly and visually, through the use of the HUD. After receiving the braking request message, the ABS module waits for brake pedal input and at that time applies maximum braking assist using the hydraulic pump motor and the HCU.

Refer to: Cruise Control - System Operation and Component Description (419-03B Cruise Control - Vehicles With: Adaptive Cruise Control, Description and Operation). Refer to: Collision Warning and Collision Avoidance System - System Operation and Component Description (419-03C Collision Warning and Collision Avoidance System, Description and Operation).

MyKey® Interaction

Through the MyKey® feature, traction control and ESC can be configured to be always on or allow the driver to select traction control and ESC on or off. When MyKey® traction control feature is configured to be always on and a MyKey® restricted key is in use, the ABS module ignores any requests made by the driver to disable traction control or ESC. In addition, when MyKey® traction control feature is configured to be always on and a MyKey® restricted key is in use, Sport mode and AdvanceTrac Off mode are not available. Refer to Disabling AdvanceTrac for information on Sport mode and AdvanceTrac Off mode. Refer to the Owner's Literature for additional information on the MyKey® feature and settings.

Stability-Traction Control Indicator (Sliding Car Icon)

Refer to: Instrument Panel Cluster (IPC) - System Operation and Component Description (413-01 Instrumentation, Message Center and Warning Chimes, Description and Operation).

Stability-Traction Control Disabled Indicator (Sliding Car OFF Icon)

Refer to: Instrument Panel Cluster (IPC) - System Operation and Component Description (413-01 Instrumentation, Message Center and Warning Chimes, Description and Operation).

One or both of the stability-traction control indicators may illuminate as a result of momentary sensor disturbances due to environmental or driving conditions (including severe vehicle maneuvers or extreme off road usage). Once Illuminated, the indicator remains illuminated until the environmental or driving condition is no longer present and