Determining the Resistance Value of the Ignition Key Resistor Pellet
From Jerry Watts, retired Corvette Engineer, National Corvette Museum:
If you own any GM car that has a resistor pellet in the key, it would be in your best interest to record the resistance value of the pellet in the vent that you lose your keys.
General Motors records the key cut, but not the resistance value of the pellet, and neither a dealer nor a locksmith can pull the resistance reading out of the computer.
To read the value of your pellet you will need a digital OHM meter. If you do not have access to one, stop by your local dealer or an electronics store and ask them to read it for you. First, set the meter to OHMs. Then, touch the tips of the leads to both sides of the key pellet. This will tell you the resistance of the particular pellet. Keep it in a safe place - just in case.