If your key has a "chip" in it the most likely cause is a broken
wire at the ignition lock. Generally not repairable-replace only, fairly expensive. Can bypass factory system by installing a
resistor with the same value as th key "chip"to small white wires wirh orange cover under the steering column. Search
net for "GM Passkey System"; you should be able to find more detailed instuctions there. I have done several, takes less
than an hour to do, works forever. Good luck, Rich.
Rich (otherair@juno.com), October 2007