GF26.00-P-0003MCU Automated Manual Transmission Shift Lever Positions, Function
GF26.00-P-0003MCU Automated Manual Transmission Shift Lever Positions, Function
TRANSMISSION 717.482
Shown with code (I75) leather sport steering wheel incl. steering wheel rocker switch system
1 Switching request
2 Transmission speed
3 Clutch request
4 Status of clutch motor
5 Request for gear change
6 Status of transmission motor
7 Engine speed
8 Reversing lamp actuation
9 Vehicle speed
10 Selector lever position
11 Accelerator pedal position
12 Status of foot brake pedal
13 Status of mechanical park pawl
14 Gear stage engaged
15 Actuation of gear indicator
A1 Instrument cluster
A45 Fanfare horns and airbag clock spring contact
E3e3 Left backup lamp
E4e3 Right backup lamp
L2 Transmission rpm sensor
M17/3 Transmission motor 1
M17/4 Transmission motor 2
M18 Coupling motor
N3/10 ME-SFI [ME] control unit
N15/5 Electronic selector lever module control unit
N15/6 Automated manual transmission control unit
N47-5 ESP control unit
S16/2 Park pawl switch
S112s1 Steering wheel gear shifter PLUS (with code (I75) Leather sport steering wheel with steering wheel rocker switch system)
S112s2 Steering wheel gear shifter MINUS (with code (I75) Leather sport steering wheel with steering wheel rocker switch system)
CAN Controller Area Network (data bus/CAN bus) (CAN)
Function
The automated manual transmission is based on a "standard" manual transmission. The shift operations are carried out by 2 selector drums which are adjusted by gear motor 1 and gear motor 2. The current position is recorded by integrated incremental sensors. The necessary clutch engagements are carried out by the clutch motor.
Operation takes place via the electronic selector lever module control unit or via the steering wheel gear shifter (with code (I75) Leather sport steering wheel incl. steering wheel rocker switch system).
The complete control of the shift processes and clutch engagements takes place by the automated manual transmission control unit.
The currently engaged gear stage as well as the gearshift recommendation are displayed in the multifunction display (A1p13) of the instrument cluster.
The following shift programs are possible:
^ Manual shift mode
The selector lever is located in the "±" plane. The gears must be selected manually.
^ Automatic mode
The selector lever is in the "D" plane. The gears are shifted automatically.
Engine start
^ Move the selector lever into position "P" and
^ actuate the foot brake and
^ Circuit 15 On
Then first the automated manual transmission control unit issues a start enable and the engine can be started with the transmitter key.
Starting off
To start off the vehicle the selector lever must be in shift plane"D" or "±":
^ Operate service brake,
^ Operate the shift lock button on the selector lever and move the selector lever into "D" or "±"
^ Release service brake
The vehicle moves off. "1"or "D" in displayed in the multifunction display depending on the shift mode selected.
Manual shift mode
The driver determines the gear change in manual shift mode.
^ Selector lever forwards "+": Upshift one gear
^ Selector lever rearwards "-": Downshift one gear
On vehicles with code (I75) Leather sport steering wheel incl. steering wheel rocker switch system the gears can also be changed via the steering wheel gear shifter:
^ Steering wheel gear shifter PLUS: Upshift one gear
^ Steering wheel gear shifter MINUS: downshift one gear
A manual downshift is only performed if it does not lead to overevving the engine.
The respective engaged gear stage is indicated in the multifunction display.
If for a driving style for an optimized fuel consumption another gear stage than the one which is engaged would be more meaningful, a gear shift recommendation from the automated manual transmission control unit appears in the multifunction display:
^ Arrow up: Shift up one gear
^ Arrow down: Shift down one gear
Forced upshift/downshift
Automatic shift operations also take place in manual shift mode:
^ Forced upshift just before reaching the maximum speed of the engine
^ Forced downshift when approaching the idle speed of the engine
^ Shift down for kickdown
^ Engage first gear when vehicle is at a standstill
Automatic mode
In automatic mode the automated manual transmission control unit determines the gear change. The shift operations run automatically (performance-map dependent) corresponding to the current load (accelerator pedal position) and vehicle speed.
The following points are taken into account for the shift operations:
^ Upshifts and downshifts are not triggered at the same operating point in order to avoid repeated shifting between two gears in the critical limits.
^ When downshifting multiple gearshifts (e.g. from 5 to 3) are also conducted.
Backup
^ Operate foot brake
^ Move selector lever into position "R"
^ Release foot brake
The vehicle moves off. "R" is displayed in the multifunction display.
The shift lock button on the selector lever must be operated for engaging reverse gear.
Kickdown function
In order to trigger an automatic downshift via the kickdown function, the accelerator pedal must be fully depressed (overcoming the over-center preload).
The following processes can be triggered based on a performance map:
^ Downshift by one to three gears
^ After this automatic upshift just before reaching the maximum speed of the engine
The kickdown function is possible in manual shift mode and in automatic mode.
Crawl function
The crawl function enables the vehicle to be driven slowly, e.g. when parking or in a traffic jam.
Function requirements:
^ Forward or reverse gear engaged
^ Accelerator pedal not actuated (engine in neutral)
Function
When the service brake is released the clutch is operated in slip or in the closed range. The vehicle then moves at a slower speed. The function is terminated by operating the service brake, parking brake, accelerator pedal or on gradients above 5 %.
Parking the vehicle
The following items must be taken into account for safely parking the vehicle:
^ Apply service brake
^ Move selector lever to position "P"
^ Operate parking brake
^ Switch off engine and remove transmitter key
^ Release service brake
If the selector lever is in position "P" the vehicle is secured to prevent it from rolling away by a mechanical park pawl. The park pawl is engaged by the electronic selector lever module control unit via a cable to the transmission The status of the park pawl is recorded by the park pawl switch and is passed on to the automated manual transmission control unit.
No gear is engaged when the engine is switched off in selector lever position "N". The vehicle can be pushed or towed away. Removal of the transmitter key is only possible in selector lever position "P".
Transmission temperature
The oil temperature influences the viscosity of the transmission oil and thus the shift operation process. As the transmission control takes into account the oil temperature for the actuation of the actuator motors, a consistent shift quality is achieved.
The temperature of the transmission is computed.
The speed of the shafts and the transmitted torque is drawn on to calculate the friction, which is converted in the transmission into heat.
The cooling due to the airstream is determined from the ambient temperature and the vehicle speed and the transmission temperature is established by means of a performance map. Following an extended immobilization period the ambient temperature is adopted for the transmission temperature.
Error reactions
The processes in the transmission are monitored by means of the actuation signals and the sensor signals. If events occur in the process which deviate from the normal sequence, these are stored in the automated manual transmission control unit. Stored events can be erased again if they do not occur any more on several trips in sequence.
There are three fault classes:
^ Fault without impairment of driving mode
^ Faults which slightly impair driving mode
^ Faults which severely impair driving mode
Fault without impairment of driving mode
Fault is stored but no effects on driving are noticeable. No warning message is output in the multifunction display. Such event recordings serve solely analysis of causes.
Faults which slightly impair driving mode
In the event of basic faults a warning message is output in the multifunction display.
The trip is only slightly impaired, the restrictions are often not noticed by the driver. Thus, e.g. overlaps and gear steps are no longer executed. The duration of the shift operations is extended.
Faults which severely impair driving mode
In the event of serious faults a warning message is likewise output in the multifunction display. The transmission changes into limp home mode.
The following reactions are possible:
- No further gearshifts are performed, the gear engaged is retained.
- Only reverse gear and 1st gear are actuated after stopping and restarting, engine performance and engine speed are limited.
- No further gear is engaged after stopping and restarting.
Initializing
The initialization must be performed using STAR DIAGNOSIS after the following activities:
^ Removal of transmission
^ Removal of one or both transmission motors
^ Replacement of automated manual transmission control unit
A transmission teach-in process takes place after the power supply is discontinued. In the process the incremental counter reading of the selector drum system of sensors is readjusted. For this purpose the selector drums are moved into their end positions when the clutch is open.
Clutch actuation
For each shift operation a clutch process is carried out by the automated manual transmission control unit. The automated manual transmission control unit actuates the clutch motor directly for this.
The load is evaluated in the automated manual transmission control unit in order to avoid overloading the clutch. If the threshold value is exceeded the clutch starts to pulse in order to draw the driver's attention to an overload. The clutch is opened in the event of further overload.
For wear adaptation the drag point and the transmission characteristics of the clutch are continuously adapted by the automated manual transmission control unit.
