Engine Starting

Unlocking the car or opening the drivers door wakes up the GM which sends a wake up call to the SMG II control unit. Awoken, the SMG II looks at hydraulic pressure stored in the accumulator. Pressure greater than 45 bar causes the SMG II to wait for starting initiation. Hydraulic pressure under 45 bar causes the SMG II to energize the hydraulic pump relay, powering up the pump to build system pressure in anticipation of a start sequence. Engine starting is only possible when the shift lever is in the 0 (idle-speed or neutral) position and the brake pedal is depressed. If a gear is selected before the key is turned to the start position of if the vehicle has been parked in gear, the shift lever must first be moved to the 0 position and the brake depressed.

Responsibility for starter operation remains with the EWS module. As the key is turned to the KL50 position, the EWS module waits for confirmation from the SMG II control unit that the shift lever position is 0 and that the brake pedal is depressed. The SMG II control unit is notified of KL50 and brake pedal position via the SMG CAN Bus by the MS S54. Receipt of notification of KL50 causes the SMG II control module to check shift lever and brake pedal position. Seeing shift lever position 0 and the brake pedal depressed, the SMG II momentarily supplies a switched ground signal to the EWS module to serve as a release to allow starter engagement. Upon receiving these confirmations the EWS module activates the starter. The clutch is open (not engaged) during start-up operation.