The ignition switch in your Chevrolet truck isn't the whole assembly on the steering column, rather just the electric switch connected to the lock cylinder. If the switch is bad (test it by turning the key and seeing if the warning lights come on), you must install a replacement switch. There can be some variations on the procedure, so consult an automotive guide for your specific year and model.
Open the hood and disconnect the negative cable from your truck's battery.
Remove the covers from the steering column by removing the screws from the bottom cover; the upper cover should come right off after the lower one. On some models, you must also remove the driver's side knee bolster.
Disconnect and remove the park lock switch from the lock cylinder housing; this is needed on some mid-size trucks like the Colorado. Disconnect the lock's electrical connector, and depress its tab with a small screwdriver to release the switch.
Insert the key, and turn it to the "On" or "Run" position. On some mid-size models you must turn it the other way into the "Accessory" position. Insert the retainer pin into the hole in the lock cylinder, and pull the cylinder out of the steering column.
Disconnect the electrical connectors for the ignition switch from the cylinder--there can be one or two of them, depending on the model, and one of them can require twisting. Then remove the switch from the cylinder by pulling out its screws.
Screw the replacement switch in position on the lock cylinder, and connect its wiring harness (or harnesses) to the electrical connector(s).
Insert the lock cylinder in the same position it was in when you removed it, aligning the lock's retainer with the slot in the steering column housing. Press the cylinder in until the retainer activates.
Replace all other components in reverse order of removal.
