Shift Interlock: Description and Operation

Interlock System (A/T)

How the Circuit Works

Key Interlock
When you push the key into the ignition switch, a ground signal is provided to the multiplex control unit. If the shift lever is in PARK, the multiplex control unit provides voltage to the key interlock solenoid, energizing the solenoid and allowing the key to be turned to the LOCK (0) position.

Shift Position Interlock
Battery voltage is supplied at all times through fuse 7 (in the under-hood fuse/relay box) to the brake pedal position switch. With the ignition in ACC (I) or ON (II), battery voltage is supplied through fuse 8 (in the under-dash fuse/relay box) to the shift lock solenoid. When you push the brake pedal, battery voltage is applied through the WHT/BLK wire to the PCM. If, at the same time, you do not push the accelerator pedal, a low voltage signal is sent through the WHT/BLU wire to the multiplex control unit. The multiplex control unit then applies ground through the YEL/BLK wire to the shift lock solenoid. The solenoid is then energized allowing the shift lever to be moved from the PARK position.

While the vehicle is in motion (in NEUTRAL, DRIVE, 2 or 1), the multiplex control unit detects the motion, and will remove ground from the shift lock solenoid. No longer energized, the shift lock solenoid will not allow the shift lever to be moved into REVERSE or PARK.