Where is the Oxygen Sensor on a 2004 GM 1500 Sierra truck?

On a 2004 GM 1500 Sierra truck, the oxygen sensors are typically located in two places: upstream (pre-catalytic converter) and downstream (post-catalytic converter). The upstream oxygen sensor is found on the exhaust manifold or just before the catalytic converter, while the downstream sensor is located after the catalytic converter in the exhaust system. To access them, you may need to raise the vehicle for better visibility. Always consult the vehicle’s service manual for specific details and locations.