Shift Interlock: Description and Operation

PURPOSE
The Shift Lock Actuator prevents the driver from shifting the automatic transaxle out of "PARK" unless the Ignition Switch is in "RUN" and the brake pedal is depressed.

OPERATION
Voltage is present at the Stop Lamp Switch at all times through the STOP Fuse. Voltage is present at the contacts of the Shift Lock Actuator relay "B" at all times through the ROOM Fuse.

Shifter Unlocking
With the Ignition Switch in "START" or "RUN", voltage is present at the coil and contacts of the Shift Lock Actuator relay "C".

With the transaxle selector lever in "PARK", the Park Sense Switch contacts are closed and the coil of the Shift Lock Actuator relay "A" is grounded.

Stepping on the brake pedal causes the Stop Lamp Switch contacts to close; voltage is now present at the coil of the Shift Lock Actuator relay "A".

The coil energizes and relay "A's" contacts close; the coils of the Shift Lock Actuator relays "B" and "C" are now grounded through relay "A". The coils of relays "B" and "C" energize and the contacts close.

Current then flows through the METER Fuse, the contacts of the Shift Lock Actuator relay "C", the Shift Lock Actuator motor and LOCKED diode, the contacts of relay "B", and the contacts of the Park Sense Switch to ground. The Shift Lock Actuator motor runs to unlock the transaxle shifter.

As the Shift Lock Actuator motor reaches the end of its cycle, it switches a contact from the LOCKED diode to the UNLOCKED diode. The UNLOCKED diode blocks further current flow and the motor stops running.

As soon as the driver presses the button on the end of the transaxle shift lever to shift out of "PARK", the Park Sense Switch contacts open and the coil of relay "A" deenergizes. The contacts of relay "A" open and the coils of relays "B" and "C" are deenergized. Voltage is present at the Park Sense Switch through the ROOM Fuse, the contacts of relay "B", the UNLOCKED diode, the motor, and the contacts of relay "C." The system is ready for locking.


Shifter Locking
As soon as the driver shifts into "PARK" and releases the transaxle shift lever button, the contacts of the Park Sense Switch close.

Current flows through the ROOM Fuse, the contacts of relay "B", the UNLOCKED diode, the motor, the contacts of relay "C", and the Park Sense Switch contacts to ground. The Shift Lock Actuator motor runs to lock the transaxle shifter.

As the Shift Lock Actuator motor reaches the end of its cycle, it switches a contact from the UNLOCKED diode to the LOCKED diode. The LOCKED diode blocks further current flow and the motor stops running. The system is ready for another cycle.