Condition change between "P" and "Not P"
In order to change the park pawl position, the TCM actuates the lift solenoid which presses the locking pin out of the catch of the piston. The piston is then pressurized on one side with hydraulic pressure in accordance with the required actuation direction, "P" or "Not P". The TCM energizes the park pawl switchover valve and thus enables the hydraulic flow to the corresponding pressure chamber for piston actuation.
NOTE:
If the power supply or hydraulic pressure control system fails, the park pawl lift solenoid can be energized via an external power supply to release the park pawl piston in order to engage the park pawl via the piston spring. It is not possible to release the park pawl without hydraulic pressure.