For models from 1999 through 2003, start by disconnecting the cable from the negative battery terminal and removing the steering column covers. Turn the ignition key to the LOCK position, then remove the ignition switch retaining screws and detach the switch. For the lock cylinder, lower the steering column after removing the retaining nuts and disconnect any electrical connectors from the immobilizer unit if equipped. To remove the clamp securing the ignition switch/key lock cylinder assembly, center-punch and drill out the heads of the two shear-head bolts, then separate the clamp and remove the assembly. Transfer the immobilizer unit from the old lock cylinder to the new one, ensuring the new lock cylinder is positioned without the key inserted, and tighten the bolts until snug. Verify the key turns in the lock cylinder, then tighten the bolts until their hex-heads break off and reconnect the immobilizer connector if applicable. For models from 2004 and later, note that the key lock cylinder/ignition switch assembly is a one-piece unit referred to as the "steering lock," which cannot be replaced separately. Begin by disconnecting the negative battery terminal and removing the steering column covers, followed by the left kick panel. Trace the electrical harness from the ignition switch/key lock cylinder assembly to the under-dash fuse and relay panel, disconnecting the electrical connector. Center-punch and drill out the shear bolts that attach the ignition switch/key lock cylinder assembly clamp to the steering column, then remove the clamp and the assembly. Install the new ignition switch/key lock cylinder assembly without the ignition key inserted, attach the mounting clamp and new shear bolts without tightening them yet. Insert the ignition key to ensure it turns freely and that the steering wheel lock functions correctly, then tighten the shear bolts until the hex heads twist off, completing the installation in reverse order of removal.