Manual (Steptronic) Mode Manual mode allows the transmission to operate as a semiautomatic 'Steptronic' unit. The driver can change up and down the five forward gears with the freedom of a manual transmission. Shift maps are provided for manual mode to protect the engine at high engine speeds. The EAT ECU will automatically change up to a higher gear ratio to prevent engine overspeed and change down to a lower gear ratio to avoid engine labouring and stalling. When kickdown is requested the EAT ECU downshifts at least 2 gears. When the vehicle is stationary, to drive off the driver can select st or 2nd gear in high range, or st, 2nd or rd gear in low range. Any other gear selection will be rejected by the EAT ECU. When driving off, upshifts can be pre-selected by making + selections with the selector lever for the number of upshifts required. The EAT ECU then automatically performs a corresponding number of upshifts when the appropriate shift points are reached. So, for example, when starting off inst gear, if three + selections are made in quick succession, the EAT ECU will automatically change up through the box to 4th gear as the vehicle accelerates, without any further selections being made. In manual mode a low gear can be selected to provide engine braking for descending a slope without HDC or continuous use of the brake pedal. The driver can prepare for the end of the descent by moving the selector lever to D. The EAT ECU will maintain the low gear and only revert to automatic shift control when the throttle is opened and vehicle speed increases.
AUTOMATIC TRANSMISSION – GM 5L40-E DESCRIPTION AND OPERATION 44-1-59 HDC Mode The HDC mode assists the ABS ECU in controlling the downhill speed of the vehicle. When HDC is selected on, the EAT ECU selects the most appropriate gear for the descent, to maximise engine braking. Cruise Mode When cruise control is activated, the EAT ECU receives a cruise active message on the CAN. The EAT ECU activates a cruise control map which prevents locking and unlocking of the torque converter clutch and minimises up and downshifts. If cruise control is operative and the vehicle speed increases due to coasting downhill, the ECM can request a downshift via a CAN message if the vehicle speed exceeds the set cruise limit. Hill Mode Hill mode is initiated by the EAT ECU when high engine torque, high throttle angle and low engine speed is detected via ECM signals on the CAN. The EAT ECU defines this combination of signals to determine when the vehicle is travelling on a steep gradient. In hill mode the EAT ECU adopts one of three shift maps which hold the transmission in low gears throughout the ascent. The shift map chosen depends on the severity of the slope as determined from the engine signals. Hill mode can also be initiated when the vehicle is at very high altitudes.