The 2006 Chevy Trailblazer 4.2L engine's camshaft position sensor (CMP sensor) is located on the
passenger side (right side) of the engine, near the front of the cylinder head. It's usually mounted on the valve cover, but can sometimes be found slightly below it, depending on specific engine variations. You'll likely need to look closely around the area between the valve cover and the timing chain cover.
To be sure, consult a repair manual specific to your vehicle's year and engine. A diagram will clearly show its location. This is much more reliable than a general description. You can usually find these online in PDF format from various sources.
