Oxygen Sensor: Description and Operation

Primary Heated Oxygen Sensor (HO2S) (Sensor 1)
The Heated Oxygen Sensors (HO2S) detect the oxygen content in the exhaust gas and signal the PCM. In operation, the PCM receives the signals from the sensor and varies the duration during which fuel is injected. To stabilize the sensor's output, the sensor has an internal heater. The Right Primary HO2S (Bank 1, Sensor 1) is installed in the right exhaust manifold, and the Left Primary HO2S (Bank 2, Sensor 1) is installed in the left exhaust manifold.