A swivel on the end of a spark plug socket and then an extension on that will get it out.
If the car will not start...the spark-plug is bad.
In a 2002 trailblazer it is located on the bottom of the radiator one the passenger side. Every other model year to my knowlege does not have drain plug.
Should be on the rear or side of the oil pan
spark plug
Under the dash
The 2005 Chevy Trailblazer has Coil-On-Plug ignition coils so there are 6 "coil packs". Each one is mounted on top of the spark plug.
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AC Delco iridiums
You need a 5/8" spark plug socket.
Turn it to the left.
follow the plug wires they are on the heads