The Throttle Position Sensor (TPS) on a 2003 Chevrolet Suburban is located on the throttle body. The throttle body itself is typically found on the intake manifold, between the air filter housing and the engine. It's a relatively small sensor, usually mounted on the side of the throttle body, and is connected by a wiring harness. You'll likely see a connector attached to it.
Because there are variations depending on the engine (e.g., 4.8L, 5.3L, 6.0L, etc.), accessing it will require looking directly at your Suburban's engine. A diagram or image of your specific engine's throttle body from a repair manual or online parts database would be helpful for precise location.
