Shift Interlock: Description and Operation

Interlock System

How the Circuit Works

Key Interlock

When the ignition key is inserted into the ignition switch, a path to ground is provided through ignition key switch to the multiplex control unit. The multiplex control unit detects that there is a key inserted into the ignition switch from this input.

When the shift lever is moved from the park position, a path to ground is provided through park pin/shift switch to the multiplex control unit. The multiplex control unit detects that the shift lever is out of park from this input. The multiplex control unit then provides voltage to the key interlock solenoid. The solenoid is then energized, which prevents the ignition switch from being rotated fully and turned to LOCK (0).

Shift Position Interlock

Battery voltage is supplied at all times through fuse 7 to the brake switch. With the ignition in ON (II) or START (III), battery voltage is supplied through fuse 10 (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 A/T shift lever to be moved from the PARK position.