System Description

The shift control system (parking lock control) electrically controls the parking lock mechanism, conventionally operated by cable, by using the actuator.

The transmission control ECU controls the shift control actuator assy, and also controls the entire system based on information from the hybrid vehicle control ECU.

The transmission control ECU detects DTCs when there are any malfunction in the system, and informs the driver of the malfunction by illuminating the P position switch indicator light and the master caution light and indicating an error message on the multi-display.

1. Operation to switch to the P position:
   1. When the P position switch is turned on to activate parking lock, a signal is sent to the hybrid vehicle control ECU.
   2. The hybrid vehicle control ECU determines whether "P lock" is possible or not based on this signal and other vehicle information.
   3. If the hybrid vehicle control ECU determines that "P lock" is possible, it sends a "P lock" operation demand signal to the transmission control ECU.
      Fig 3: Locating P Position Switch Indicator Light

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   4. Receiving the signal, the transmission control ECU activates the shift control actuator assy in order to lock the parking lock mechanism and turns on the P position switch indicator light.
   5. At that time, the transmission control ECU controls motor rotation angle based on signals from the rotation angle sensor in the shift control actuator assy.
   Fig 4: Identifying Cycloid Reduction Mechanism

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   HINT:

   In the cycloid reduction mechanism, the output shaft is linked to the external gear. Together, they rotate only a single tooth when the eccentric adapter, which is linked to the motor, rotates once. Driving force is increased like this so that the parking lock mechanism can be switched even when high output is required for parking on a hill, etc.

   Fig 5: Identifying Selector Lever

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Operation to switch to a non-P position:
   1. When the hybrid system is started (the vehicle is ready to be driven) and the selector lever is moved to the R, N, or the D position with the brake pedal depressed, a signal is sent to the hybrid vehicle control ECU.
   2. This signal is then sent from the hybrid vehicle control ECU to the transmission control ECU as a "P lock release" operation demand signal.
      Fig 6: Identifying P Position Switch Indicator Light

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   3. Receiving the signal, the transmission control ECU activates the shift control actuator assy in order to unlock the parking lock mechanism and turns off the P position switch indicator light.
   4. At that time, the transmission control ECU controls motor rotation angle based on signals from the rotation angle sensor in the shift control actuator assy.
3. SHIFT POSITION CHANGE FUNCTION 
   1. The shift control system (parking lock control) comprehensively determines vehicle conditions and changes the shift position, as shown in the following chart, by cooperating with the shift control function of the hybrid system (except when the reject function, described later, is in operation).
   2. Other than indicated in the following chart, when the power switch is turned off with the vehicle stopped, the shift position is automatically changed to the P position.
   Fig 7: Shift Position Change Function Table

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
4. REJECT FUNCTION 

In the shift control system (parking lock control), there may be a situation in which a shift change cannot be done for safety reasons. When attempting to move the selector lever in such a situation, the system sounds a reject buzzer inside the meter and changes the shift position as shown in the following table.