Circuit Operation, Ignition Key Interlock

On vehicles equipped with the interlock safety feature the vehicle must be in park and the transfer case in high or low gear before the key can be removed from the ignition. If the gear selector or transfer were Out of gear, the key must be cycled before removal.

If the vehicle is not in park, voltage from Fuse B2 is applied to the Ignition Key Switch and Solenoid (X177) through the closed contacts of the Transmission Range Selector Switch (Z110). When the ignition switch is placed in the 0 position, the switch in the Ignition Key Switch and Solenoid closes to energize the solenoid and prevent key removal.

If the transfer box is in the neutral position. Interlock Relay 1 (K153) is de-energized, since the relay coil is not grounded by the Transfer Box Position Switch. When the relay is de-energized, voltage is applied to the Ignition Key Switch and Solenoid (X177) through the relay's switch contacts causing the solenoid to energize and prevent key removal.