Gear Shift, Function - GF27.60-P-2000KJ

TRANSMISSION 700.4 in MODEL 453.0/3/4 

Function requirements for shift operation, general 

• Circuit 15 ON
• Transmission not in limp-home mode
• Engine not in limp-home mode
• Drive train CAN (CAN C) signals

Shift operation, general 

The dual-clutch transmission (DKG) control unit (N15/13) records, for example, the actual and necessary target gear based on the following sensors and information:

• Transmission mode recognition sensor (B56/1)
• Selector lever position from electronic selector lever module control unit (N15/5) over the drive train CAN
• Rpm sensor 1, transmission input shaft with direction detection (B108)
• Rpm sensor 2 transmission input shaft (B109)
• Brake lights switch (S9/1)
• Steering wheel downshift button (S110/1) over steering wheel clock spring contact (A45/1)
• Steering wheel upshift button (S111/1) over steering wheel clock spring contact
• Accelerator pedal position from accelerator pedal sensor (B37) over ME-SFI [ME] control unit (N3/10) and drive train CAN (CAN C)
• Wheel speeds, from left front axle rpm sensor (L6/1), right front axle rpm sensor (L6/2), left rear axle rpm sensor (L6/3), right rear axle rpm sensor (L6/4) over the Electronic Stability Program control unit (N30/4), interior CAN (CAN B), drive train CAN with the ME-SFI [ME] control unit interface

Displays in the instrument cluster (A1)

The gear indicator (A1 p12) is shown to the driver in the instrument cluster's multifunction display (A1p13). The gear indicator information is sent by the dual clutch transmission control unit over the drive train CAN, ME-SFI [ME] control unit, interior CAN to the instrument cluster.

The shift function is divided up into the following function sequences:

• Function sequence for shifting up and down 
• Temporary transmission mode "M", function sequence 
• Function sequence, shifting from 1st gear to 2nd gear 
• Function sequence for actuation during shift operation 

Function sequence for shifting up and down 

The dual clutch transmission control unit actuates the clutch actuator 1 (M14), clutch actuator 2 (M15) and the actuators for the internal gearshift to match the incoming signals.

Temporary transmission mode "M", function sequence 

In the temporary transmission mode "M", the driver can select the following functions by pressing the steering wheel downshift button or steering wheel upshift button:

• Pressing the steering wheel downshift button once causes the transmission to shift to a gear below the gear currently engaged.
• Pressing the steering wheel upshift button once causes the transmission to shift to the next higher gear.

The individual gears "", "1", "2", "3", "4", "5", "6" can thereby be selected individually. The reverse gear and neutral position can only be shifted to through the electronic selector lever module. The signals from the steering wheel downshift button and the steering wheel upshift button are sent directly to the dual clutch transmission control unit.

Downshifts that would result in an rpm that could damage the engine are suppressed until the maximum rpm drops below a threshold value stored in the characteristics map of the ME-SFI [ME] control unit.

Function sequence, shifting from 1st gear to 2nd gear 

If 1st gear is engaged and the vehicle drives in 1st gear, then the following components are involved at the same time:

• The clutch is engaged, clutch actuator 1 is then actuated by the dual clutch transmission control unit
• The park pawl is locked in the "Not P" position and the lock pawl is lifted out of the park pawl gearing
• The actuators of the internal gearshift are actuated by the dual clutch transmission control unit and the shift fork is shifted towards 1st gear

If now the shift into 2nd gear takes place, the following components are involved at the same time:

• The 1st gear idler gear remains engaged. The dual clutch transmission control unit is not actuated
• The shift motor is actuated by the dual clutch transmission control unit, and the shift fork is hydraulically shifted towards 2nd gear
• Clutch actuator 2 is actuated by the dual clutch transmission control unit.

  Clutch actuator 1 is now deenergized and the vehicle moves in 2nd gear. Clutch actuator 2 energization is increased proportionally to the reduction in control current at clutch actuator 1, thereby ensuring a smooth gearshift operation. The shift fork is shifted into the center position and 1st gear is disengaged

Function sequence for actuation during shift operation 

To engage a gear, the shift motor must be actuated. The sliding sleeves are then shifted by the shift forks. Actuation is provided by the dual clutch transmission control unit.

	Electrical function schematic for gearshift function		PE27.19-P-2057-97BBA
	Overview of system components for dual clutch transmission		GF27.10-P-9994KJ