Just the Facts: Oxygen (O²) Sensors What does an Oxygen Sensor do? The Oxygen or O2 sensor outputs a voltage between .1 volt and 1 volt based on the amount of oxygen in the exhaust. The computer uses this rich or lean information to trim the air/fuel ratio for the most efficient operation. Where are these sensors located? The Oxygen sensor is located directly in the exhaust stream in the exhaust manifold. Will a malfunctioning Oxygen Sensor illuminate the check engine light or affect vehicle operation? Yes, a failing sensor can illuminate the MIL, and will cause the vehicle to have poor performance, poor mileage and possibly black smoke emitting from the tailpipe. What are the common causes of failure? Silicone entering the combustion chamber, oil and water leaks on the sensor or wiring can cause the sensor to fail. The O2 sensor internal heater can fail due to normal usage. How to determine if these sensors are malfunctioning. The Oxygen sensor can be monitored for proper voltage range and proper switching frequency with a scan tool. It is recommended that if the vehicle has an oxygen sensor in each exhaust manifold both sensors should be replaced when one has failed. What makes Standard Oxygen Sensors the best. One-piece laser welded body for maximum protection and precise operation maintaining sensor integrity Dual internal talc seal makes Standard Oxygen sensors last longer Breathable Teflon membrane allows increased air flow for a faster switch rate to improve fuel economy and save the motorist money at the pump Stainless steel shield protects the element from thermal shock and regulates proper air flow to ensure faster sensor response and better performance View our 21st Century Tune-Up® video video Back to Just the Facts