Design
DesignControl module/gear-shift position sensor
The transmission control module (TCM). and the gear-shift position sensor form one unit. This unit is mounted on the top of the transmission housing, on the gear shift linkage rod. The control module connector is directly connected to the transmission.
The gear-shift position sensor provides the transmission control module (TCM). with information about the gear selected and whether back-up (reverse) gear is selected so that the back-up (reversing) lamps can be lit if required. The gear-shift position sensor contains a permanent magnet and a linear Hall sensor. The gear-shift position sensor generates a signal voltage between 0 and 5 V. This signal voltage corresponds to the currently selected gear selector lever position. There are diagnostics for the gear-shift position sensor.
Voltage level for the different gears
P = 0.65 V
R = 1.64 V
N = 2.12 V
D = 2.49 V
Shift solenoids S1, S2, S3, S4 and S5
The shift solenoids S1, S2, S3, S4 and S5 are positioned in the valve body in the transmission control system, which is mounted on the front edge of the transmission. The shift solenoids (on/off type), consist of an electrical coil which controls a hydraulic valve. The solenoids are supplied with 12 V via the transmission control module (TCM). and grounded in the control system. The shift solenoids control shifting. The transmission control module (TCM). determines which gear is to be used by activating them in different patterns. There is a diagnostic for the shift solenoids.
Lock-up solenoid, SLU
The lock-up solenoid, SLU is in the transmission control system. This is on the front edge of the transmission. The lock-up solenoid, SLU, consists of an electrical coil which controls a hydraulic valve. The solenoid is controlled by pulse width modulation (PWM) voltage. The solenoid is grounded via the transmission control module (TCM). The solenoid controls lock-up engagement of the torque converter. During engagement, the solenoid pulses which ensures smooth engagement of the lock-up function. The solenoid allows the torque converter to work in one of three positions: Open, Controlled slipping and Locked. The hydraulic function of the solenoid is linear. There are diagnostics for the solenoid.
Line pressure solenoid, SLS
The line pressure solenoid, SLS is in the transmission control system, which is mounted on the front edge of the transmission. The line pressure solenoid, SLS consists of an electrical coil which controls a hydraulic valve. The solenoid is controlled by pulse width modulation (PWM) voltage. The solenoid is grounded via the transmission control module (TCM). The hydraulic function of the solenoid is linear. The hydraulic valve is controlled by the varied current which is the result of the pulse conditions. During high pulse conditions, (at high currents (approximately 1 A)) the line pressure is low. During low pulse conditions (at low currents) the line pressure is high. In the event of an open-circuit the line pressure reaches maximum which causes hard shifting. The hydraulic valve is then completely open. There are diagnostics for the solenoid.
Line pressure solenoid, SLT
The line pressure solenoid, SLT, is in the transmission control system. This is on the front edge of the transmission. The line pressure solenoid, SLT, consists of an electrical coil which controls a hydraulic valve. The solenoid is controlled by pulse width modulation (PWM) voltage. The solenoid is grounded via the transmission control module (TCM). The hydraulic function of the solenoid is linear. The hydraulic valve is controlled by the varied current which is the result of the pulse conditions. During high pulse conditions, (at high currents (approximately 1 A)) the line pressure is low. During low pulse conditions (at low currents) the line pressure is high. In the event of an open-circuit the line pressure reaches maximum which causes hard shifting. The hydraulic valve is then completely open. There are diagnostics for the solenoid.
Transmission input speed sensor (speed of the input shaft)
The transmission input speed sensor (input shaft speed ) is on the upper side of the transmission housing. The sensor is an active sensor and is supplied with 12 V. When the pulse wheel on clutch C1 rotates, the sensor generates a pulsed current (quadratic wave) where the strength of the current depends on the position of the pulse wheel. The signals from the coil in the sensor are then effected by a magnetic resistance element, which generates a current which oscillates between 7 mA and 14 mA, and the frequency of which increase with speed. The transmission control module (TCM). calculates the transmission input speed using the signal from the sensor. The transmission control module (TCM). uses information about the input shaft speed to calculate the torque reduction to be requested from the engine control module (ECM) when shifting. The value is also used to compare the engine speed (RPM) with the speed of the input shaft in order to calculate the slipping rate of the torque converter. The value is also compared with the transmission output speed sensor signal in order to calculate the actual gear ratio. This is done to check whether the value corresponds to the expected gear ratio. There are diagnostics for the transmission input speed sensor.
Transmission output speed sensor (speed of the output shaft)
The transmission output speed sensor (speed of the output shaft) is on the reverse of the transmission housing. The sensor provides signals to the transmission control module (TCM) about the vehicle speed. The output shaft speed sensor is an active sensor and is supplied with 12 V. When the pulse wheel (wheel for shift-lock) rotates, the sensor generates a pulsed current (quadratic wave) where the strength of the current depends on the position of the pulse wheel. The signals from the coil in the sensor are then effected by a magnetic resistance element, which generates a current which oscillates between 7 mA and 14 mA, and the frequency of which increase with speed. The control module calculates the transmission output speed using the signals from the sensor. The signal is compared with the signal from the transmission input speed sensor and is used to calculate the gear ratio and is also used for diagnostics. There are diagnostics for the transmission output speed sensor.
Oil temperature sensor
The temperature sensor is an NTC sensor. The temperature sensor is on the transmission control system inside the side cover. It gauges the temperature of the transmission fluid in the oil pan. The temperature sensor is integrated in the cable harness. The temperature sensor is supplied with 5 V and is grounded via the transmission control module (TCM). The control module can determine the transmission fluid temperature by measuring the voltage drop across the NTC resistor of the sensor. The control module stores the time the temperature has been within a certain temperature range. If a certain temperature and time has been exceeded, a diagnostic trouble code (DTC) indicating that a oil change is necessary is stored. There are diagnostics for the temperature sensor.
Gear selector module (GSM)
The gear selector assembly is in the tunnel console. It is mechanically connected to the transmission by a cable which moves the gear valve in the transmission control system. The gear selector module (GSM) is on the top panel of the gear selector assembly. The gear selector module (GSM) is powered by the transmission control module (TCM). The gear selector module (GSM) uses serial communication to communicate with the transmission control module (TCM) to light the gear position indicator for example. The gear selected is indicated by a row of LEDs in the top panel on the gear selector assembly.
There is a directly connected cable from the transmission control module (TCM) to the gear selector module (GSM) which controls the shiftlock solenoid. The power supply and ground for the shift-lock solenoid are directly connected to the gear selector module (GSM). The winter mode switch (W) is in the top panel on the gear selector assembly. When pressed, the switch transmits a request to activate winter mode to the transmission control module (TCM). The transmission control module (TCM) then determines whether winter mode can be engaged or not.
There are diagnostics for the gear selector module (GSM). In the event of a fault, a signal about the fault status is transmitted to the transmission control module (TCM) where any diagnostic trouble codes (DTCs) are stored.
Gear selector assembly
Gear selector assembly with Geartronic function
Gear selector assemblies with Geartronic are unique in appearance and function. In addition to P/R/N/D modes they also have a manual (M) shifting mode. The gear selector for Geartronic has the following functions:
- P: Park position
- R: Back-up (reverse)
- N: Neutral
- D: Automatic shifting between all gears. (Does not apply when the mode selector is in winter mode (W), for further information see, Function/Shifting program/Winter mode)
- M: Manual shifting. There are three Hall sensors on the gear selector module (GSM). A permanent magnet on the cover in the gear selector lever affects the output signals of the Hall sensors to the gear selector module (GSM).
Function
Controlling the shift solenoids when shifting
The solenoids are activated in a specific pattern to control shifting and the lock-up function. Solenoids S1-S5 determine which gear is to be used. Solenoids SLS, SLU and SLT determine engagement by adjusting the hydraulic line pressure. The basic parameters for the different shifting points are the accelerator pedal (AP) position and the vehicle speed. The shift quality is decided by controlling the torque. 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). Two shifting patterns can be selected, normal conditions and winter mode (selected using the W button).
In normal conditions, shifting and lock-up occur at relatively low engine speeds to reduce fuel consumption. In the event of rapid accelerator pedal movements, the transmission control module (TCM). automatically shifts to sport mode.
Shifting program
Economy mode
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. In addition the transmission oil pressure is adjusted to provide smooth gear engagement.
Sport mode
The transmission switches from economy mode to sport mode if the accelerator pedal (AP) is pressed down quickly. The conditions are that the throttle opens and the vehicle speed exceeds 50 km/h. As soon as the accelerator pedal (AP) is moved less quickly economy mode is resumed. In the sport mode shifting program the shifting points are adjusted to provide the best possible performance. Down shifting occurs at lower engine speed (RPM).
Extreme mode
At wide open throttle (WOT) the kick-down function is engaged and the transmission shifts to the lowest possible gear. In this way a boost of power is achieved when overtaking for example.
Winter mode
Winter mode is selected using the (W) button on the top panel of the gear selector assembly. Winter mode enables starting off in a high gear to prevent the wheels from spinning on a slippery surface. This mode can also be used in other difficult situations in which the driver needs more direct control over gear selection. When D is selected, the car starts in 3rd gear. There is automatic shifting between 3rd, 4th and 5th gears.
When winter mode is selected a W lights on the dashboard. If kick-down is activated in Winter mode, the transmission uses all gears for maximum performance.
Other modes
Adaptation
The transmission control module (TCM) monitors each shift during all driving conditions to fulfill consistent and smooth shifting. 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:
- throttle opening is steady
- oil temperature between 65°C and 110°C
Temperature controlled lock-up
If the transmission temperature increases abnormally as a result of heavy load under high ambient temperature conditions, the torque converter lock-up function is activated as often as possible (temperature controlled lock-up). This reduces slippage and the generation of heat in the transmission. The lock-up function will not be used if the temperature drops below +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 in position D or M
- gear 3, 4 or 5
- the transmission input speed is 1100 rpm or more and the throttle opening is 20-35% depending on the engine version
- the transmission oil temperature is 40-120°C
Due to the torque converter slipping between 50-200 rpm, the friction properties of the transmission fluid are very important. The transmission fluid differs from conventional ATF oil properties. Always use the specified fluid for this transmission. Failure to do so may compromise the function and set a diagnostic trouble code (DTC). The engine coolant must reach a certain temperature before the function engages.
Driving uphill
The transmission control module (TCM). may change the gear shift pattern slightly when driving uphill. This is to avoid busy shifting.
Shifting using Geartronic
When the gear selector is moved to Geartronic mode (M), 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 M mode. The transmission control module (TCM). transmits a signal to the gear selector module (GSM) to light the M LED and switch off the other LEDs. The transmission control module (TCM). determines if the shift can take place. 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 1st, 2nd and 3rd gears can be selected. 4th gear can be selected at speeds in excess 30 km/h and 5th at speeds in excess of 40 km/h
- The kick down function is only available in the D position
- Automatic down shifting occurs for all gears below a certain speed. Example: 2nd gear is selected. Automatic down shifting occurs when shifting from 2nd gear to 1st at 2 km/h if the speed, before this, has exceeded 25 km/h. Otherwise 2nd gear is maintained. For example, there may be situations when 2nd or 3rd gear is engaged despite the car being stationary. Manual up shifting is required after automatic down shifting
- The permitted engine speeds for manual down shifting corresponds to those for kick-down up shifting, i.e. engine speeds of approximately 6,000 rpm
- If the transmission temperature becomes too high, the transmission control module (TCM) determines the shift timing. The purpose is to maintain a gear where lock-up is possible at the current speed
- Lock-up is possible in 3rd, 4th and 5th gears. (1st and 2nd gears do not have lock-up).
Other
In position M, the signal indicating the position of the lever to the gear selector module (GSM) is generated as follows: For each of the three gear selector positions there is a Hall sensor on the printed circuit board for the gear selector control module (GSM). A permanent magnet on the cover in the gear selector lever affects the output signals from the sensors to the control module. The control module can read off the position of the lever through the differences in the signal characteristics.
Shift-lock
To avoid any chance of the gear selector inadvertently moving from the P or N position, the car is also equipped with an electrically operated shift-lock function. This locks the interlock pin in the gear selector lever in the shift-lock section, locking the selector lever in the P or N position.
From P to another gear position
To move the gear selector from the P position, the ignition must be switched on and the brake pedal depressed. (The stop lamp switch is activated.). The transmission control module (TCM) retrieves the brake pedal position via the CAN network and the currently selected gear from the internal gearshift 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. There is a Hall sensor in the gear selector assembly which is affected by a permanent magnet on the cover of the assembly. 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 O the solenoid is deactivated. The gear selector is mechanically locked in position P by breaking the power supply to the solenoid.
From N to another gear position
To move the gear selector from the N position, the ignition must be switched on and the brake pedal depressed. (The stop lamp switch is activated.). The transmission control module (TCM). retrieves the brake pedal position via the CAN network and the currently selected gear from the internal gearshift 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 N, the solenoid is deactivated and the lock pin slides in. The gear selector can be moved to positions D and M as normal. However the lock button on the gear selector must be pressed before R or P can be selected. When the ignition is in position I or O, the solenoid is deactivated.
Shift-lock override
The mechanical lock mechanism in the gear selector assembly can be overridden so that the gear selector can be moved when the power is off or in the event of an electrical fault. A small tool can be inserted under a cover on the gear selector assembly panel to release the gear selector.
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). A signal is sent 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. This prevents the car from lurching forwards when started.
Adaptation data
There are two functions for adaptation in the transmission control module (TCM) software which can be activated:
- Resetting adaptation - carried out after replacing internal components or the entire transmission
- Adaptation function - This function helps the mechanic to adapt the transmission. This makes it easier to reset the function of the transmission after repair or replacement of, for example:
- the transmission control system
- the transmission fluid
- the entire transmission
- transmission control module (TCM).
When the adaptation function has been activated, the test drive instructions must be followed. The following shifts can be adapted:
- 1-2
- 2-3
- 3-4
- 4-5
- N-D
- 5-4
- 4-3
- 3-2
- 2-1
- N-R.
While the function is activated, the general warning lamp in the combined instrument panel indicates when each shift has been adapted to its target value.
When the general warning lamp (triangle) flashes after each shift, the adaptation is complete.
Adaptation of the transmission is activated via the VIDA vehicle communication socket.
Counter for transmission fluid 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 reset function is activated via the VIDA vehicle communication socket.
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 remedy).
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.