Function
Function
Regulating the solenoids when gearshifting
Gearshifts are regulated by means of the Transmission Control Module (TCM) activating the solenoids in specific patterns. The solenoids S1, S2, SLC1, SLC2, SLC3 and SLB1 control which gear shall be engaged. The solenoids SLC1, SLC2, SLC3 together with solenoid SLT also control how the engagement shall take place by means of adapting the hydraulic pressure. The basic parameters for the differences in gearshift timing are the position of the accelerator pedal and vehicle speed, while the gearshift quality is determined by the torque steer.
The pressurization of the clutches and the brakes is adjusted by reading the changes in speed of the transmission input shaft during the shifting process and comparing them to the values calculated in the transmission control module (TCM).
In normal conditions shifting takes place at relatively low rpms to reduce fuel consumption. At higher acceleration/throttle Transmission control module (TCM) automatically switches to another shifting program. These shifting programs are based on engine type.
*) with engine braking
Regulating the lock-up function
Regulating the lock-up function takes place by means of the Transmission Control Module (TCM) activating the lock-up solenoid. The engagement takes place by means of the Transmission Control Module (TCM) controlling the lock-up solenoid linearly and adapting the hydraulic pressure. The basic parameters for engagement are the engine speed, accelerator pedal position and the rotation speed of the transmission input and output shafts. The pressurizing of the lock-up function can be adapted by means of reading off the changes in the rotation speed of the transmission input shaft during the gearshift processes and comparing them with the calculated values in the Transmission Control Module (TCM).
Two different lock-up functions are integrated: locked lock-up and slipping lock-up.
Locked lock-up
In normal conditions lock-up takes place at relatively low speeds in order to reduce fuel consumption.
The function locked lock-up only works when the transmission's temperature is above 20 °C.
Slipping lock-up
This function ensures smoother engagement with reduced vibration and decreased noise when a gear is engaged. In this mode, the torque converter clutch is engaged, but not fully locked.
The following conditions must be met in order for the function to activate:
- gear selector lever in D or MAN
- gear 2, 3, 4, 5 or 6
- transmission's input speed is between 1,000 rpm and up to approx. 2,000 rpm
- transmission oil temperature is 20 - 120 °C.
Due to the slipping of the torque converter, 50 rpm, the friction properties of the transmission oil are very important. The transmission oil's properties therefore differ from conventional ATF oil properties. Always use transmission oil specified for this transmission, otherwise the function of the transmission can be impaired.
Gearshift program
Normal program
When driving at normal acceleration, the transmission control module (TCM) uses a pre-set shifting program, optimized to shift for economy driving. This shifting program is suitable for "normal" driving which provides earlier up shifts and lock-up.
The shifting program adapts automatically to different driving scenarios, for example:
- driving on grade with trailer
- driving at high elevation
- driving in warm climate
- driving with poor fuel quality.
Also, the transmission's oil pressure is adapted to give smooth engagement of the gears.
Driving uphill
Transmission control module (TCM) can also change shifting pattern during driving on an uphill grade. This is to avoid frequent shifting. Then shifting takes place at higher rpm.
Driving downhill
Shifting points are adjusted to obtain more engine brake when driving on downhills.
Sport mode (only certain engine versions)
The sport mode is achieved by shifting the gear lever from D to the right to the end position at +/-.
At the same time, the symbol in the combined instrument panel display changes from D. Usually a downshift occurs as soon as S mode is active.
Driving in S mode gives a more sporty feeling when driving actively. Shifting occurs at higher engine speeds compared with driving in D mode. During active driving, a lower gear is prioritized, which means delayed upshifts.
Shifts to a higher gears also take place faster and more distinct. The transmission has an adaptive function which means that it adapts to the driving in sport mode.
The starting point in sport mode, calm driving, is that shifting points are the same as for normal driving but with more sensitive pedal.
The gearbox is manual, Geartronic mode, when the gear lever is moved forwards or backwards in manual mode. The information display symbol changes then from S to the engaged gear, 1-6.
Other modes
Adaptation
The transmission control module (TCM) monitors each shift during all driving conditions to fulfill consistent shifting, smooth shifting in normal mode as well as hard shifting in sport mode. This is carried out by the control module either lowering or increasing the hydraulic line pressure used during the shift itself. The changed pressure levels are stored in the control module memory when the car has been switched off and are retrieved on start-up. This provides improved shifting comfort and increased service life.
Complete adaptation occurs when the following conditions have been met:
- the position of the accelerator pedal is constant
- oil temperature between 65 °C and 110 °C.
Driving uphill
The Transmission Control Module (TCM) can change the gearshift pattern slightly when driving uphill. This is to avoid close gearshifts.
Neutral control (only available on certain models)
This function is activated when the driver stops the car and the car is stationary, at traffic lights for example. The transmission control module (TCM) then partly disengages the C1 clutch which releases the forward drive of the transmission and reduces the load on the engine. The function improves fuel consumption and reduces vibrations at idle speed. When the driver releases the brake, the C1 clutch engages and drive is resumed.
The following conditions must be met in order for the neutral function to activate:
- gear selector in position D
- oil temperature above + 10 °C
- accelerator pedal position less than 3%
- brake pedal depressed
- speed 0 km/h
- engine speed (RPM) less than 1500 RPM.
Alternative driving programs
There are driving programs that are implemented in the transmission but that only are active on certain variants.
Kick-down
When the accelerator pedal is pressed down past a certain point, the Kickdown function is activated. This means that downshifting takes place to get faster acceleration. The pedal position for Kickdown is designated as 110%.
Quick step
Quick step makes the gearshifting function sportier when the driver is more aggressive on the pedal. Lower gears are used for better acceleration.
Fast Off
Fast Off is used to reduce the number of shifts due to heavy traffic in, e.g., city traffic.
The function is activated at fast releases of the accelerator pedal. Even the vehicle's speed, brake pedal, and curve detection affect its function. By keeping a lower gear than normally, unnecessary shifts are avoided. For aborted passing, a lower gear is maintained to be able to take the initiative for future passing.
Curve hold
The function Curve hold can block upshifting in case of curves to get better traction out of curves, for example, when driving in roundabouts.
Brake shift
Adjusts shifting points according to brake pressure. The purpose is to have a lower gear when accelerating after braking.
Gearshifting with Geartronic
When the gear selector is moved to the Geartronic position (+/-) the automatic transmission remains in hydraulic position D. When the gear selector is moved upwards (+) the gear selector module (GSM) transmits a signal to the transmission control module (TCM) to shift up. When the gear selector is moved downwards (-), a signal is transmitted to the transmission control module (TCM) to shift down. The driver information module (DIM) switches the symbol in the combined instrument panel from D to the current gear, for example 3, when the gear selector is in manual mode. A signal is also sent to the gear selector module (GSM) to light both the +/- LEDs and switches off the other LEDs. The transmission control module (TCM) determines if the shift can take place and the Driver information module (DIM) indicates the current gear. If shifting is permitted the solenoids are activated according to each specific gear pattern.
However, in certain situations the transmission control module (TCM) takes over responsibility for determining shifting. The follow applies:
- When stationary, only gears 1, 2 and 3 can be selected. Gear 4 can be selected at speeds above 40 km/h and gear 5 at speeds above 55 km/h, and gear 6 at speeds above 70 km/h. Speeds may vary due to engine version.
- Automatic downshifts take place on all gears when below a certain speed. Example: Gear 2 is selected. Automatic downshifting then takes place from gear 2 to gear 1 at 2 km/h if the speed before this exceeded 25 km/h. Otherwise gear 2 remains engaged. However, situations can arise where gear 3 remains engaged despite the vehicle stopping.
- Manual upshifting is required after automatic downshifting. Kickdown is not available in manual gear mode (+/-).
- Downshifting at Kickdown is permitted in manual gear mode (Geartronic).
- Permitted rpms for manual downshifting correspond to the rpms for upshifting in kickdown.
- If transmission temperature becomes too high then the Transmission Control Module (TCM) takes over the gearshift decisions. The purpose of this is to engage a gear where lock-up is possible at the current speed.
- Lock-up is possible for gears 2, 3, 4, 5 and 6.
Miscellaneous
In manual gear position (+/-) a signal is generated on the position of the gear selector lever for the Gear Selector Module (GSM) in the following way: there is a Hall sensor fitted on the printed circuit board for the Gear Selector Module (GSM) for each one of the three gear selector lever positions. A permanent magnet on the gear selector lever acts on the sensors' output signals to the control module. The control module can read off the position of the gear selector lever by means of the differences in signal character.
Shift-lock
Shiftlock
To prevent the gear selector from accidentally being moved from P- or N-position, the vehicle also features an electrically operated lockout function (shiftlock). The shiftlock function unlocks the gear selector's lock in P-position and locks the shiftlock in N-position. In this way the gear selector is passively locked in P-position (inactive solenoid) and actively locked in N-position (active solenoid).
From P position to another gear position
In order to shift the gear selector from the P position to another gear position the ignition must be on and the brake pedal depressed (stop lamp switch activated). The transmission control module (TCM) retrieves the brake pedal position via the CAN network and the currently selected gear from the internal gear-shift position sensor. The signal is then transmitted from the transmission control module (TCM) to the gear selector module (GSM) to control the solenoid (electro magnet) in the gear selector assembly.
When the gear selector is in position P, the solenoid is activated and the lock pin slides in. The gear selector lock button can be pressed down as usual to select another gear. The Gear Selector Module (GSM) is in the gear selector assembly with a Hall sensor, which is affected by a permanent magnet
The Hall sensor is deactivated when the gear selector is moved from position P. The shift-lock solenoid is disengaged at the same time. This prevents the gear selector from sticking in position N. When the ignition is in position "I" or "0" the solenoid is deactivated. The gear selector is mechanically locked in position P by breaking the power supply to the solenoid.
From N position to another gear position
In order to shift the gear selector from the N position to another gear position the ignition must be on and the brake pedal depressed (stop lamp switch activated). The transmission control module (TCM) retrieves the brake pedal position via the CAN network and the currently selected gear from the internal gear-shift position sensor. The signal is then transmitted from the transmission control module (TCM) to the gear selector module (GSM) to control the solenoid (electro magnet) in the gear selector assembly.
With the gear selector in N, the solenoid is deactivated and unlocks the gear selector's interlock. One can then press the release button in the gear selector lever to engage D or M. The release button on the gear selector lever must be pressed to select R or P. The solenoid is deactivated when the ignition switch is in position "I" or "0".
Shiftlock override
In order to maneuver the gear selector assembly from P mode when its power is cut off or if there is an electrical fault, the lock mechanism in the gear selector assembly can be mechanically overridden. Under a cover on the gear selector assembly panel, a narrow tool can be inserted to release the gear selector.
The Transmission Control Module (TCM) has also an automatic shiftlock function (override) in order to control the gear selector to the locked P mode and from locked N mode in the event of an electrical fault.
Park / neutral position (PNP) function
The car has a park/neutral position (PNP) function to prevent the starter motor from turning when a gear is selected. This function is controlled by the transmission control module (TCM), which receives a signal from the gear selector module (GSM) indicating that the gear selector is in position P or N. The park / neutral position (PNP) function ensures that the starter motor can only be activated when the gear selector is in position P or N.
Adaptation data
The Transmission Control Module (TCM) software includes a service for resetting adaptations that can be activated:
- Resetting adaptation - should be performed after replacing an internal component or the whole transmission.
Resetting adaptation is activated via the vehicle communication input.
Gauge for transmission oil data
A counter for transmission oil quality is built into the software for the transmission control module (TCM). The counter counts up the amount of time the oil is above a certain temperature. When the counter has reached the maximum value, the diagnostic trouble code (DTC) for an oil change is stored in the control module. When replacing transmission fluid, the counter must be reset to prevent a diagnostic trouble code (DTC) being stored incorrectly. This applies when the transmission fluid is changed and when the fluid is changed during a repair.
The resetting function is activated via the vehicle communication input.
Emergency mode in the event of a fault
An emergency program is activated to deal with the fault when the transmission control module (TCM) detects a transmission fault (permanent fault). The transmission control module (TCM) then implements certain corrective actions to protect the transmission, while leaving the car in the best possible drivable condition. Minor malfunctions do not activate an emergency program. There are different programs depending on the type of fault.
- Emergency/limp-home mode
- Fail-safe action (temporary action)
The fail-safe action is indicated as soon as the fault is detected. Normal function is resumed if the fault disappears. Emergency mode is activated for minor faults and the Limp home mode for the most serious faults. If the malfunction is intermittent, the transmission control module (TCM) returns to normal operation the next time the ignition is switched on.
The warning lamp in the combined instrument panel lights and a text message appears in the display in the combined instrument panel if emergency/limp home mode is engaged. No text is displayed until the fault has been detected when the ignition is switched on.