Shift Interlock: Description and Operation

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.

Voltage is present at the Stop Lamp Switch at all times through the STOP Fuse. Voltage is present at the contacts of 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 Shift Lock Actuator relay "C". With the transaxle selector lever is PARK, the Park Sense Switch contacts are closed and the coil of 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 Shift Actuator relay "A". The coil energizes and relay "A's" contacts close; the coils of 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 flows through the METER Fuse, the contacts of Shift Lock Actuator relay "C", the Shift Lock Actuator motor and LOCKED diode, the contacts of relay "B" and the contacts of 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 form 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 blocks further current flow and the motor stops running. The system is ready for another cycle.