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Home >> Mini >> 2006 >> Cooper (R50) L4-1.6L (W10) >> Repair and Diagnosis >> Transmission and Drivetrain >> Continuously Variable Transmission/Transaxle >> Description and Operation >> Electro Constantly Variable Transmission (ECVT) >> Group Three

Group Three



Group Three Elements
These elements are externally connected to other systems.

- Ratio Control Motor
- Park/Neutral Switch
- Output Shaft Speed Sensor
- Instrument Cluster Display
- Selector Shift Mechanism
- Steering Wheel Remote Buttons (Optional)
- GIU (gearbox interface unit)

Group Three Components
Ratio Control Motor

The Ratio Control Motor is housed inside the transmission, adjacent to the oil cooler pipe connections. The motor and solenoids are connected to the main harness via a circular connector. The motor is operational in all transmission modes and controls the hydraulic control unit to adjust the primary pulley to the appropriate position.
The motor which controls the transmission ratio is a linear actuator and a bi-polar stepper motor.

Park/Neutral Switch
The selector cam activates the park/neutral switch, which prevents the car from starting in reverse or drive and switches on the reverse lights when in reverse. The switch status is also used by the EMS2000 in conjunction with the gear selector switch to establish the correct driving mode.

The switch is operated by a cam, which also operates the hydraulic control unit within the transmission. The selector lever via a cable to the transmission operates the cam. The switch has two positions and performs several functions, one of which is to inform the EWS immobilization unit that the transmission is in the park or neutral positions. The EWS unit will then enable the starter relay coil to be energized, thus allowing the engine to be started.

When the selector lever is in the park or neutral position and the ignition is switched on, the EMS2000 will energize a shift lock solenoid on the selector lever. This locks the lever in the park or neutral position. The selector lever cannot be moved from the park or neutral position until the footbrake is applied.


Output Shaft Speed Sensor
The ECVT transmission has a dedicated secondary speed sensor located in the differential housing. This sensor is a Hall effect sensor and produces a pulse train of approximately 73000 pulses per mile. The sensor allows for more precise calculation of transmission output speed that is used in the control strategy systems.
The secondary speed sensor is located so that the sensor tip is close to the crown wheel of the differential. By sensing the crown wheel, the signal is not affected by the different wheel speed signals when the vehicle is cornering.


Instrument Cluster Display
A Liquid Crystal Display in the instrument cluster shows the current drive mode and selected gear. The display includes the following characters, 'P', ' R', ' N', ' D', ' SD', ' 1', ' 2', ' 3', ' 4', '5', ' 6' and EP. During Adaptations "X" will be displayed in front of the normal character (e.g XP).

Selector Mechanism
Selection of the required driving mode, through the selector lever inside the vehicle, activates a selector shaft within the transmission. A push/pull type cable connects the lever in the car and the shaft on the gearbox. A cam fitted to the selector shaft is also connected to the manual valve of the control system, and selects one of its five desired positions (PRNDS/M). Moving the selector lever across the gate trips a proximity sensor.


A spring and cone operated pawl mechanically locks the secondary pulley when the selector lever is moved to the Park position. If selection of park is made at speed the pawl will rattle without engaging Park. It will not engage until the vehicle speed drops below approximately 3 mph.

Movement of the selector lever (or steering wheel buttons) in a forward direction, plus (+), changes the transmission up the gear ratios and movement in a rearward direction, minus (-), changes the transmission down the gear ratios.


GIU (Gearbox Interface Unit)
The main function of the GIU is to allow communication between the ECVT and the EMS2000. The GIU has the following functions:

- Conversion of inputs from the selector lever switches (and steering wheel switches if fitted) into a CAN instruction that is read by the EMS2000.
- Drive the LED's to display transmission mode.
- Conversion of the CAN instruction for the EMS2000 into electrical signals to drive the ratio control motor, clutch and secondary pressure solenoids.

Gearbox Interface Unit Inputs
There are many inputs the GIU requires for correct functionality:

- Selector lever switches.
- Steering wheel switches (if fitted).
- Park/Neutral switch.
- CAN messages from the EMS2000.

Selector Lever Switches
The park, reverse, neutral and drive switch is located on the left-hand side of the selector lever, secured to the base plate with two screws. The switch is connected to the main harness by a ten-pin connector.

The park, reverse, neutral, drive and manual switch has four proximity sensors that correspond to the four selector lever positions. Two further proximity sensors correspond to the manual +/- positions. The selector lever has two targets, upper and lower. The upper target is aligned with the park, reverse, neutral, drive and manual sensors and the lower target aligns with the +/- sensors.

When the selector lever is moved to the manual/sport position, the upper target moves away from the drive proximity sensor. The GIU senses this and puts the transmission into manual/sport mode. The transmission will operate in sport mode until the GIU senses that either the + or the - proximity sensor is operated; the GIU will then operate the transmission in manual mode.


CAN Communication
The communication between EMS2000 and GIU is by CAN. The EMS2000 talks directly to the ECVT interface GIU via the CAN link. The GIU sends the EMS2000 information on the following:

- The current status of the park, reverse, neutral and drive switches.
- The current status of the sport/manual switches.
- The current status of the +/- switches (steering wheel buttons if fitted).
- The current status of the +/- switches (selector lever).
- Fault status of all active components.
- The current status of the Park/neutral switch.

The EMS2000 provides information for the transmission GIU via a CAN-bus. The EMS2000 controls the position of the ratio control motor indirectly (by means of instructing the GIU to control the motor to a given position). The EMS2000 can interrogate the GIU for fault diagnostics and to request real time data and system performance checks when the vehicle is connected to DISplus.






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