Auto Hold

The auto hold feature is activated and deactivated through the use of the auto hold switch located in the SYNC touchscreen. For the system to activate, the vehicle must not be moving, the driver safety belt must be buckled and the driver door must be closed.

The ABS module receives the driver safety belt buckle status from the RCM, driver door status from the BCM, while brake system pressure and the wheel speed are received from the ABS sensors. This information allows the ABS module to determine if the vehicle is stopped. Once the previous conditions have been met, the auto hold feature can be activated. When the switch is pressed, the APIM module sends an auto hold message to the GWM over the HS-CAN3. The GWM relays the message to the ABS module over the FD-CAN.

The ABS module then sends a message to the IPC through the GWM indicating the auto hold feature has been activated and the IPC illuminates the auto hold indicator.

The auto hold indicator illuminates when the IPC receives a message from the ABS module through the GWM.

Once the auto hold feature is activated and the driver presses the brake pedal, the ABS module closes the isolation valves in the EBB unit to maintain the current brake system pressure at the wheel ends. The ABS module maintains the pressure until the driver presses the accelerator pedal, shifts the transmission into PARK or after a specific time limit has been reached. The ABS module engages the parking brake after 2-10 minutes, depending on the grade of incline the vehicle is currently stopped on; the steeper the grade, the shorter the time.