Where is low pressure ac port on 2003 Chevy impala?

The low-pressure AC port on a 2003 Chevy Impala is typically located on the dryer/accumulator. The dryer/accumulator is usually found near the firewall, on the passenger side of the engine compartment. It's often a smaller fitting, sometimes with a blue cap.

However, the exact location might vary slightly depending on the specific model and trim level. It's always best to consult a repair manual specific to your 2003 Chevy Impala to be absolutely certain. You can find these manuals online or at auto parts stores. A visual inspection with the help of a diagram will be the most accurate way to identify it.