2015 Buick Enclave Owner Manual - Page 226

Driving and Operating While in L (Low), the transmission will prevent shifting to a lower gear range if the engine speed is too high. You have a brief period of time to slow the vehicle. If vehicle speed is not reduced within the time allowed, the lower gear range shift will not be completed. You must further slow the vehicle, then press the − (Minus) button to the desired lower gear range. Automatic Engine Grade Braking is not available when the ERS is active. It is available in D (Drive) for both normal and Tow/Haul mode. While using the ERS, cruise control and the Tow/Haul mode can be used. See "Tow/Haul Mode" following. 9-25 Tow/Haul Mode _ (Tow/Haul): If equipped with Tow/Haul mode, the button is on the center stack under the climate controls. Press the button to activate the system. Press it again to deactivate the system. This feature can assist when towing or hauling a heavy load. When Tow/Haul is activated, the Tow/Haul symbol will come on in the instrument cluster. See Driving Characteristics and Towing Tips on page 9-46. Automatic Engine Grade Braking Automatic Engine Grade Braking assists when driving on a downhill grade. It maintains vehicle speed by automatically implementing a shift schedule that uses the engine and the transmission to slow the vehicle. The system will automatically command downshifts to reduce vehicle speed, until the brake pedal is no longer being pressed. While in the Electronic Range Select (ERS) mode, grade braking is deactivated, allowing the driver to select a range and limiting the highest gear available. Grade braking is available for normal driving and in Tow/Haul mode. See Automatic Transmission on page 9-22.