GM has used transponder chip keys on relatively few models. Do not confuse transponder
chip keys with the earlier VATS/PASS keys which contain a visible resistor pellet. GM
original transponder chip keys have either a PK3, PK3+ or just a "+" stamped on them.
GM PK3 keys may be duplicated by one of two methods. The first method is a simple on-board procedure using a properly cut and coded duplicate along with an existing key. An alternate method is to clone the code to a special blank which contains a read-write chip. The second method does not necessitate having to program the vehicle.
PK3+ keys cannot be cloned, but are programmed using an on-board procedure.
With duplication or origination, there is no need to connect the vehicle to programming equipment.
An exception to the standard GM keys is the Cadillac Catera. This is a European made car with a totally different key, which may be cloned to duplicate.