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The voltage generated by the sensor must be greater or less than the voltage of the damping zone to send a rich or lean signal to the controller. Some­times referred to as “block learn,” it adjusts the cycle time of the fuel injector. The sensor’s analog input to the controller is converted to a digital rich or lean command to drive a fuel trim software program. The controller uses 450mV as a midpoint in a voltage range to control fuel trim for the injector pulse cycle. The ideal point is 0.45 V (450 mV) DC this is where the quantities of air and fuel are in the optimum ratio, which is called stoichiometric. A reading of 0.8 V (800 mV) DC represents a rich mixture where there is little or no oxygen in the exhaust stream. Two platinum (Pt) electrodes are placed on the ZrO2 to provide a connection for output voltage to a control module.Īn output voltage of 0.2 V (200 mV) DC represents a lean mixture where there is oxygen in the exhaust stream. The Greek letter lambda is used to describe the voltage range of the sensor when it compares the quantity of oxygen in the exhaust relative to oxygen in the atmosphere. The oxygen sensor – originally called a lambda sensor – is made of zirconium oxide (ZrO2), a chemical compound used to form the sensor’s thermal-driven electrochemical fuel cell. Oxygen Sensor 101 Did you ever wonder when that chemistry or physics class could come in handy? The knowledge from these studies can help you understand a problem with a fuel delivery system. Knowing how the oxygen sensor operates and what makes up the exhaust gasses that flow past the sensors and through the catalytic converter can help in determining when to replace and prevent future problems. The current federal OBD II warranty period for an oxygen sensor is two years or 24,000 miles, whichever comes first, but with proper care and the right fuel diet, the oxygen sensor should be a maintenance-free emissions system component. The pre-catalytic converter oxygen sensor is used for fuel trim and the post-catalytic converter oxygen sensor is used to monitor converter efficiency. The pre- and post-catalytic converter oxygen sensors are part of these requirements. 1, 1996, OBD II became a global requirement.

A single sensor was installed into the exhaust stream to modify fuel delivery and maintain catalytic converter efficiency. Oxygen sensors were first used for fuel trim and emissions in the late 1970s and into the mid-1990s.