Here it the procedure for 're-learning' the master key for my Chevy Malibu. I assume that most Chevy's that have a transponder work this way well:

1. With an unlearned master vehicle key, turn ON the ignition, but not the engine:

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2. Wait for roughly 10 minutes (mine was slightly longer) for the 'security indicator' to turn off:

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3. Turn the ignition completely OFF and wait for roughly 5 seconds.

4. Repeat steps 1-3 for two more times for a total of 3 cycles (roughly 30 minutes)

NOTE: it is important to complete all steps of the third cycle, especially step three, as this is how the vehicle learns the key transponder information. In other words, before starting the car, you must turn off the ignition and wait 5 seconds first.

5. With the key you just programmed, turn the key and start the car. The key is now operable on the car.

Warning: all other keys you may have previously had will no longer work, and must be re-programmed as well.

In order to reprogram additional keys:

  1. Take the master vehicle key that is already programmed, and turn the ignition to ON (with engine OFF)
  2. Watch the 'security indicator' until it's solid
  3. Turn the ignition off and quickly replace the key you wish to program
  4. Turn the ignition to ON (engine OFF) and wait until the 'security indicator' turns solid
  5. The Key is now programmed and should now start the car