The ignition switch lock cylinder is set into the housing farthest from the ignition and lets the key rotate to five different positions. Accessory, off (locked), Unlock, On/Run and Start. If there is a column shift on the car, you'll need to replace the interlock cassette when you install the cylinder, but for a floor shift, the interlock cable should be altered at the driver's floor shifter. Check the first thing with a lock is if it is factory-locked; if it is, then disconnect the negative cable from the battery and then the upper and lower covers from the steering column and take off the lever alongside the screw that holds it in place. Put the ignition key into the run spot and push down the retaining tab, then push the tab and pull the lock cylinder out. Push the key into the lock and turn it to start the mechanism to relieve pressure on the retaining tab. Guide the shaft at the edge of the lock cylinder directly into the socket in the housing, seeing that the socket is set to Run. Place the lock cylinder inside the housing, with its grooves lined up and push it so the tab shows from the other end. Turn the Off button and take the key out. If a column shift vehicle has received a new lock cylinder, place and adjust a new interlock cassette; for a floor shift vehicle, reposition or place the adaptor on the interlock cable. After that, put back on the upper and lower covers on the steering column, put the tilt lever in place and fix the negative cable to the battery.