Ignition Switch: Description and Operation

KEY-IN IGNITION SWITCH
The key-in ignition switch is concealed within and integral to the ignition switch, which is mounted on the steering column. The key-in ignition switch is actuated by the ignition lock cylinder mechanism, and is hard wired between a body ground and the Body Control Module (BCM) through the instrument panel wire harness.

The key-in ignition switch cannot be adjusted or repaired and, if faulty or damaged, the entire ignition switch unit must be replaced.

The key-in ignition switch closes a path to ground for the BCM when the ignition key is inserted in the ignition lock cylinder, and opens the ground path when the key is removed from the ignition lock cylinder. The BCM monitors the key-in ignition switch status through an internal pull-up, then sends the proper switch status messages to other electronic modules over the Programmable Communications Interface (PCI) data bus network. The key-in ignition switch status is also used by the BCM as an input for chime warning system operation.

IGNITION SWITCH AND KEY LOCK CYLINDER
The electrical ignition switch is located on the steering column. It is used as the main on/off switching device for most electrical components. The mechanical key lock cylinder is used to engage/disengage the electrical ignition switch.

Vehicles equipped with an automatic transmission and a floor mounted shifter: a cable is used to connect the interlock device in the steering column assembly, to the transmission floor shift lever. This interlock device is used to lock the transmission shifter in the PARK position when the key lock cylinder is rotated to the LOCKED or ACCESSORY position. The interlock device within the steering column is not serviceable.

If the ignition key is difficult to rotate to or from the LOCK or ACCESSORY position, it may not be the fault of the key cylinder or the steering column components. The brake transmission shift interlock cable may be out of adjustment.

Vehicles equipped with an automatic transmission and a steering column mounted shifter:an interlock device is located within the steering column. This interlock device is used to lock the transmission shifter in the PARK position when the key lock cylinder is in the LOCKED or ACCESSORY position. If it is difficult to rotate the key to or from the LOCK or ACCESSORY position, the interlock device within the steering column may be defective. This device is not serviceable. If repair is necessary, the steering column assembly must be replaced.

Vehicles equipped with a manual transmission, a floor mounted shifter, and a LEVER below the ignition key: A lever is located on the steering column behind the ignition key lock cylinder. The lever must be manually operated to allow rotation of the ignition key lock cylinder to the LOCK or ACCESSORY position. If it is difficult to rotate the key to the LOCK or ACCESSORY position, the lever mechanism may be defective. This mechanism is not serviceable. If repair is necessary, the steering column assembly must be replaced.

Vehicles equipped with a manual transmission, a floor mounted shifter, and NO LEVER below the ignition key: The ignition key cylinder must be depressed to allow it to be rotated into the LOCK or ACCESSORY position. If it is difficult to rotate the key to the LOCK or ACCESSORY position, the lock mechanism within the steering column may be defective. This mechanism is not serviceable. If repair is necessary, the steering column assembly must be replaced.