Where is the thermostat located on a 2002 Chevy Trailblazer straight 6?

The thermostat on a 2002 Chevy Trailblazer with the inline-6 engine (4.2L) is located at the very back of the engine, on the passenger side. It's often somewhat difficult to access and requires removing some components to get to it properly. You'll likely need to work around various hoses and possibly the intake manifold.