Where is the 2009 chevy cobalt o2 sensor located?

The 2009 Chevy Cobalt has two oxygen sensors in the exhauSTSystem. The bank one sensor is located at the bottom of the exhaust manifold just before the catalytic converter. The second one is immediately after the catalytic converter. The only tool you will need to remove them is a 22-millimeter open end wrench or an oxygen sensor wrench. You might want to warm the engine for a while before trying to remove them that way the metal can swell on the exhaust potentially making it easier to remove. Unplug the electrical connection first then rotate the sensor counterclockwise to unscrew it and remove it. New sensors will cost between 30 and $35 each and if you have a shop replace them, labor charges could be as much as $80 per hour.