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

Transmission 725.096 in model 213 

up to model year 2021 

Function requirements for shift operation, general 

• Circuit 15 ON
• Internal combustion engine running.
• Engine speed from ME-SFI [ME] control unit (N3/10)
• Vehicle speed signal
• Automatic transmission not in limp-home mode
• Complete and fault free signal transmission over drive train CAN (CAN C1)

Shift operation, general 

To check the function requirements, the fully integrated transmission control unit (Y3/8n4) reads in the following signals via the drive train CAN:

• Circuit 15 ON from the electronic ignition lock control unit (N73) via chassis FlexRay (Flex E) and powertrain control unit (N127)
• Running combustion engine from the ME-SFI [ME] control unit
• Motor rpm from the ME-SFI [ME] control unit
• Vehicle speed from the instrument cluster (A1) via user interface CAN (CAN HMI), electronic ignition lock control unit, chassis FlexRay and powertrain control unit

The ME-SFI control unit transmits the status of the engine management to fully integrated transmission control unit via drive train CAN.

The Electronic Stability Program control unit (N30/4) sends the signal from the operational drivetrain to fully integrated transmission control unit via chassis FlexRay, powertrain control unit and drive train CAN.

The fully integrated transmission control controller unit (Y3/8) converts the electrical signals coming from the fully integrated transmission control unit into hydraulic signals.

Gear ranges "R", "N", "D1" to "D9" and "P" can be engaged by operating the DIRECT SELECT lever (S16/13).

The DIRECT SELECT lever sends the information on the selected gear range "P", "R", "N", "D1" to "D9" via the steering column tube module control unit (N80), which then sends the signal to the chassis FlexRay. The signal is registered by the powertrain control unit and sent via the drive train CAN to the fully integrated transmission control unit.

The corresponding gear range is then engaged.

The shift range for engaged gear range "D1" to "D9" is shown on the instrument cluster.

Although the shift range can be changed in the forward gears while driving, the fully integrated transmission control unit prevents a shift operation if the engine speeds are too high or too low.

Messages and displays in instrument cluster 

Information about the selected gear, the gear range or the transmission mode is made available on the drive train CAN by the fully integrated transmission control unit. The powertrain control unit receives and forwards it via chassis FlexRay, electronic ignition lock, user interface CAN to the instrument cluster. This then actuates the relevant display via the following signals:

Multifunction display (A1p13) 

• Gear indicator, actuation
• Transmission mode display, actuation

  The following components are switched on by the fully integrated transmission control unit:

• Park pawl lift solenoid (Y3/8l1)
• Lubrication pressure solenoid (Y3/8y12)
• K81 clutch control solenoid (Y3/8y13)
• K38 clutch control solenoid (Y3/8y14)
• K27 clutch control solenoid (Y3/8y15)
• B08 multidisk brake control solenoid (Y3/8y16)
• B05 multidisk brake control solenoid (Y3/8y17)
• B06 multidisk brake control solenoid (Y3/8y18)
• Working pressure solenoid (Y3/8y19)
• Wet clutch solenoid (Y3/8y22)

  The following signals are processed by the fully integrated transmission control unit:

• Pressure sensor (Y3/8b5)
• Turbine wheel rpm sensor (Y3/8n1)
• Input speed rpm sensor (Y3/8n2)
• Output shaft rpm sensor (Y3/8n3)
• Transmission oil temperature sensor (Y3/8s2)
• Park pawl position sensor (Y3/8s4)

Function sequence for shift operation 

The function sequence is described in the following steps:

• Function sequence for shifting up and down 
• Function sequence for 1 to 2 shift 

Function sequence for shifting up and down 

The basic shifting program can be influenced by the driver via the DYNAMIC SELECT switch (N72/4s1), which is located in the area of the center console in the left lower control panel (N72/4). The left lower control panel sends the signal over the LCP LIN (LIN A3), Audio/COMAND control panel (A40/9), telematics CAN (CAN A), head unit (A26/17), user interface CAN, electronic ignition lock control unit and the suspension FlexRay to the AMG sports suspension control unit (N3/43) (with code 466 (Active engine mount) or with code 467 (Electronic locking differential) up to model year 2018) or to the Drive Unit control unit (N145/1) (except code 466 (Active engine mount) or except code 467 (Electronic locking differential) up to model year 2018 or as of model year 2018). The AMG sports suspension control unit or the Drive Unit control unit sends the information for the selected transmission mode to the chassis FlexRay. The powertrain control unit receives this information and transmits it via the powertrain CAN to the fully integrated transmission control unit.

The following transmission modes are available:

• Comfort
• Sport
• Sport+
• Individual
• Race (only for models 213.089/289)

The manual shift mode button (N72/4s12) can be used to select the "manual shift mode".

By pressing the steering wheel downshift button (S110/1) or the steering wheel upshift button (S111/1) in the transmission modes, the driver can select the following functions:

• The short-term M mode is activated by pressing the steering wheel gearshift buttons in the transmission modes. This allows the driver to change gear using the steering wheel gearshift buttons without having to select the short-term M mode beforehand. The previous gear limitation/shift into optimum gear function using the steering wheel gearshift buttons has been discontinued.
• The short-term M mode is automatically deactivated again after a specific period. This time interval starts again after every additional press of a button. The activity of the function is extended depending on the wide open throttle and lateral acceleration involved.
• In transmission mode "C", in comparison to the transmission modes "S" and "S+", a shorter shift range (shifting at low engine speed) and therefore a lower drive torque is available when starting off forwards and starting off in reverse. This allows for more economical and comfortable driving because the gears are not driven to the limit.

The reverse gear and neutral gear can only be shifted to using the DIRECT SELECT lever. The park pawl (gear range "P") is activated by operating the park pawl on the DIRECT SELECT lever.

The status of the steering wheel downshift button and the steering wheel upshift button is read in by the fully integrated transmission control unit over the steering wheel electronics (N135), steering wheel CAN (CAN LR) (as of 01.06.2018) or the steering LIN (LIN E1) (up to 31.05.2018), steering column tube module control unit, suspension FlexRay, powertrain control unit and the drive CAN.

Function sequence for 1 to 2 shift 

Multidisk brake B05, multidisk brake B06 and multidisk clutch K38 are engaged in 1st gear. When shifting from 1st gear to 2nd gear, multidisk brake B05 is disengaged and multidisk clutch K81 is engaged.

The shift operation can be started by the fully integrated transmission control unit. Here, the multidisk brake B08 is filled and the pressure in multidisk brake B08 is increased continuously. Simultaneously the pressure in multidisk brake B06 is reduced.

This involves a flowing transition. When the 2nd gear torque is reached, the engine speed must be adapted to the 2nd gear level (elevation phase).

This speed adjustment is achieved by the pressure in the multi-disk brake B08 being increased and, if necessary, engine torque being reduced via the ME-SFI [ME] control unit.

A forced downshift occurs at excessively low rpm and a forced upshift occurs at an excessively high rpm. If the vehicle is stationary, 1st gear is automatically selected. It is possible to start off both in 1st or 2nd gear.

Short-term M program 

The short-term M mode is a temporary mode that is activated when the steering wheel gearshift buttons are operated. Pressing in the positive (+) direction triggers an upshift and pressing in the negative (-) direction triggers a downshift, insofar as this is permissible. If not, the current gear is maintained. After a specified time window, this function deactivates again automatically. The activated time can be extended by undershooting a minimum speed (e.g. stopping), upon recognition of a lateral acceleration or if the vehicle is in deceleration mode. If none of the stated criteria are active anymore, the short-term M mode remains active for a specified period of time. After this remaining time has elapsed, a switch is made back to the initial shift program. In addition, the driver is shown a recommended shift operation in the instrument cluster. This is part of the gearshift recommendation that is also integrated. The driver can prematurely cancel the short-term M mode through specific actions, e.g. if he/she presses and holds the steering wheel upshift button in the "positive" direction (+), if the gear range changes or if he/she changes the transmission mode. If one of these preconditions is met, a switch is made back to the initial shift program.

Shifts, which could result in non-permissible high or low engine speeds, are not performed.

	Electrical function schematic for shift operation		PE27.19-P-2057-97DAS
	Overview of system components of automatic transmission (AT)		GF27.10-P-9992ANO