Transmission Control Systems: Description and Operation

DESCRIPTION AND OPERATION
The electronic control system consists of the Transmission Control Module (TCM), sensors, a linear solenoid and four solenoid valves. Shifting and lock-up are electronically controlled for comfortable driving under all conditions. The TCM is located on the insulator center bulkhead, behind the driver's seat.

Shift Control
Shifting is related to engine torque through the linear solenoid which is controlled by the TCM, and is used to operate the throttle valve.
The TCM instantaneously determines which gear should be selected by various signals sent from sensors, and actuates the shift control solenoid valves A and B control shifting. Also, Sport Shifting mode has been adopted to shift gears up and down manually in [3/M] position with using the shift switch on the steering column's right pod.




The combination of driving signals to shift control solenoid valves A and B is shown in the table above.




Sport Shifting (Manual Shifting) Mode
In [3/M] position, the driver can use the shift switch on the steering column's right pod to shift gears up and down; much like a manual transmission.

- Pushing up on the shift switch: Transmission upshifts to the next higher gear.
- Pushing down on the shift switch: Transmission downshifts.

The number of the selected gear is displayed in the shift indicator next to the [M] indicator.

- Automatic shifting control in Sport Shifting mode

This position also has automatic shifting areas:

- 1-2 upshift
- 4-3 downshift, 3-1 downshift, 2-1 downshift

depending on vehicle speed. To prevent engine over-revving, the transmission has a 1-2 automatic upshift speed, and 4-3, 3-1, 2-1 downshift allowable speeds.

- When the vehicle reaches the 1-2 automatic upshift speed, the TCM outputs the 1-2 upshift signal to the transmission and the transmission upshifts to 2nd from 1st gear.

- When the vehicle is coasting over the 4-3 downshift allowable speed and 3-2 downshift allowable speed, the TCM does not input the downshift signal from the shift switch, and the transmission does not downshift.

- When the vehicle is coasting over the 2-1 downshift allowable speed in 2nd gear, the TCM inputs the signal to wait until it reaches the 2-1 downshift allowable speed, then the shift indicator blinks to indicate it is waiting to downshift to 1st.


When the vehicle decelerates to a stop, the transmission shifts to 1st gear automatically.

The transmission can be shifted to 2nd gear by pushing the shift switch up while the vehicle is stopped. Therefore, the vehicle can start off in 2nd gear.

Lock-up Control
From sensor input signals, the TCM determines whether to turn the lock-up ON or OFF, and activates lock-up control solenoid valve A and/or B accordingly.

The lock-up control mechanism comes into operation in 2nd, 3rd and 4th, in [D] and [3/M] positions.




The combination of driving signals to lock-up control solenoid valves A and B is shown in the table above.