What size wrenches are needed to remove the catalytic converter on a 2003 Chevrolet Impala?

There's no single answer to what size wrenches are needed to remove a catalytic converter on a 2003 Chevrolet Impala. The size will depend on the specific fasteners used by the manufacturer. They might even vary slightly between different production runs of the same year and model.

You should expect to need a variety of wrenches, including:

* Oxygen sensor sockets: You'll likely need an oxygen sensor socket (usually a thin-walled socket to avoid damaging the sensor) to remove the oxygen sensors before removing the catalytic converter. The size is typically 7/8" or 22mm, but could be different.

* Wrench(es) for the catalytic converter bolts: These bolts are usually 13mm, 15mm, or 18mm. You might need both metric and SAE sizes just in case. Some bolts could even be different sizes on the same converter.

* Socket wrench set: A complete socket set will help you determine the correct size by trying them on each bolt.

* Wrench(es) for the exhaust pipes: You might need wrenches to loosen clamps or bolts connecting the pipes to the catalytic converter. Sizes vary.

Before you start:

* Consult a repair manual: A repair manual specific to your 2003 Chevrolet Impala will give you the most accurate information on wrench sizes and the proper removal procedure. This is highly recommended to avoid damaging your vehicle.

* Inspect the bolts: Before you start, look at the bolts carefully to determine the size(s) needed.

Attempting this without the proper tools and knowledge can lead to damage to your vehicle. If you're not comfortable working on your car, it's best to take it to a qualified mechanic.