How do you reset the change oil light on a 2002 Trailblazer?

Turn on you ignition without starting the engine. Press on the gas pedal 3 times, all the way down. NOT TOO FAST OR TOO SLOW. The light should then go off.

From the 2002 Trailblazer owner's manual:

If your Trailblazer/Envoy is equipped with the Driver Information Center at the bottom of the instrument cluster:

1) Change your oil filter and oil.

2) Turn on your ignition without starting the engine.

3) Navigate to the oil life 0% display using the fuel info button (gas pump icon).

4) Push / hold the select button (arrow icon) until it resets back to oil life 100% (+/-10 seconds)

5) Take a test drive and drop off your used oil at a recycling station...