Pre-CAT Heated Oxygen Sensors

Description

The Heated Oxygen Sensor (HO2S) produces a voltage that varies between 100 mV and 900 mV under the normal operating conditions. On the Catera, the full operating range of the HO2S circuit is approximately from 200 mV to 1,200 mV. The Engine Control Module (ECM) monitors this voltage and determines if the exhaust is lean or rich. The oxygen sensor voltage is high when the exhaust is rich, and low when the exhaust is lean. The ECM constantly monitors the HO2S signal during the closed loop operation and compensates for a rich or lean condition by decreasing or increasing the injector pulse width as necessary.

Function

The main function of the fuel control heated oxygen sensors is to provide the control module with the exhaust stream information in order to allow for a proper fueling and to maintain the emissions within mandated levels. After the sensor reaches the operating temperature, the sensor will generate a voltage, inversely proportional to the amount of the oxygen present in the exhaust gases. The control module uses the signal voltage from the fuel control heated oxygen sensors in a closed loop operation in order to adjust the fuel injector pulse width. While in a closed loop operation, the ECM can adjust the fuel delivery in order to maintain an air/fuel ratio which allows the best combination of emission control and driveability.

Oxygen Sensor Pigtail

If there is damage to the oxygen sensor pigtail wiring, the connector or the terminal, you must replace the entire oxygen sensor assembly. Do Not attempt to repair the wiring, the connector or the terminals. The sensor will need a clean air reference in order for the sensor to function properly. This clean air reference is obtained by way of the oxygen sensor wire(s). Any attempt to repair the wires, the connectors or the terminals could result in the obstruction of the air reference and degrade the oxygen sensor performance.

HO2S Heater

Heated oxygen sensors are used in order to minimize the amount of time that is required to obtain a closed loop fuel control operation and to allow for an accurate catalyst monitoring. The oxygen sensor heater greatly decreases the amount of time that is required for fuel control sensor HO2S 1 to become active. The catalyst monitor sensor HO2S 2 oxygen sensor heater is required by the to maintain a sufficiently high temperature. This allows accurate exhaust oxygen content readings from the engine.