Where are the two O2 sensors located on a 1997 Chevy Camaro?

There are four oxygen sensors on a 1997 Camaro V8. They are located on the lower part of the exhaust manifolds, two towards the front of the engine and two towards the rear. The front sensors are referred to as the upstream sensors and are heated (indicated by 4 wires leading to the sensor). The rear sensors are called the downstream sensors and are not heated (indicated by only one wire leading to the sensor).