You don't GM uses what is known as a vats system there is a small resistor built in the key it makes contact with both sides of the ignition lock when you put the key into lock .The cars Computer then reads the key and if all is well the car will start.Some times the key just needs to be replaced with a new one and sometimes it's the ignition lock the wires on the inside break and in some cases it's the cars computer, a new key is about 15 dollars,a new ign lock will run about 55 and the computer will cost around 1200.00 try the key first call or go by a locksmith shop first you should get the best deal there they should also be abel to do the lock cyl unless you have the tools to do it yourself.Hope this helps.