Lambda Sensor
It is not difficult to understand what anoxygen sensordoes. It is harder to believe, though, the benefits it provides. In spite of its small size-slightly larger than a spark plug-the oxygen (O2) sensor in a vehicle greatly contributes to reduce fuel consumption and to keep the natural environment free of hazardous exhaust emissions. Yet, this sensor has a simple structure and configuration designed to either emit or resist a small electrical current, a signal the vehicle’s computer uses to make some important engine management decisions.Oxygen sensor locationThe oxygen sensor can be located either on the exhaust manifold or somewhere along the exhaust pipe. Depending on your particular sensor and vehicle model, this device may have one or more electrical wires coming out of one end. The tip at the other end, exposed to the exhaust stream, is where the sensor’s operating element is located. Some vehicles come equipped with up to five, even more in some cases, of these sensors.Primary and secondary oxygen sensorsAlthough all oxygen sensors perform the same function, a vehicle’s computer may use data from a particular O2 sensor to monitor a component’s performance as well. This function helps to classify oxygen sensors in a vehicle as primary and secondary. A primary O2 sensor’s job is to monitor oxygen content in the exhaust stream before it reaches the catalytic converter and is positioned closer to the engine. On the other hand, a secondary O2 sensor checks for oxygen content in the exhaust stream right before it enters the catalytic converter. This helps the computer confirm that the primary sensor is in working order. Alternatively, a secondary oxygen sensor can be located on the other side of the catalytic converter, monitoring the converter’s job by examining oxygen content in the exhaust stream as it leaves the device.What an oxygen sensor does?Before the oxygen sensor can even get to work, though, it needs to reach its operating temperature, usually around 600 F (315 C). To speed up its warming process, some sensors come equipped with a heating element. Until the sensor reaches its proper temperature, the vehicle’s computer operates in “open loop” mode, ignoring any signal coming from the oxygen sensor(s). Once the O2 sensor(s) reaches operating temperature, the computer changes to “close loop” mode, and begins to monitor the voltage signal(s) coming from the sensor(s).The electrical signal leaving the oxygen sensor varies constantly within a 0.10 to 0.90 volts range, approximately. When the signal reaches the high end of its range, the computer knows the sensor has detected high oxygen content in the exhaust stream and uses this information to make necessary adjustments to increase fuel delivery. In turn, this action from the computer triggers a low voltage signal from the sensor, telling the computer it has detected low oxygen content. The computer makes the necessary adjustments to lower fuel content and the cycle begins, repeating itself continually to maintain a proper amount of fuel delivery to the combustion chambers.Types of oxygen sensorsThere are basically two types of oxygen sensors in used today:Zirconiaand titania oxygen sensors. An O2 sensor with a zirconia-sensing element allows this device to produce its own voltage signal to communicate with the vehicle’s computer. The small voltage it generates is the result of the difference between the oxygen content detected in the exhaust stream and the oxygen content in the atmosphere surrounding the sensor. This is the most popular type of sensor.An O2 sensor with a titania sensing element allows this device to act as a resistor against the voltage supplied to it by the computer. How much resistance the sensor produces depends on the amount of oxygen content in the exhaust gas stream. The reduced voltage signal is then returned back to the computer. A titania type of sensor has a faster response rate than a zirconia one. Both types, however, are equally effective in aiding the computer to determine the best air/fuel ratio based on the voltage signal sent by the sensor(s).How long does an oxygen sensor last?An oxygen sensor’s service life usually ranges from 50,000 to 100,000 driving miles, depending on the type of sensor. However, two key factors can contribute to shorten significantly its life: Carbon buildup and contamination. Carbon builds up around the tip of the sensor-the end of the device exposed to the exhaust stream-due to a rich fuel condition in the mixture. This may indicate problems in the fuel injection system for which the computer is unable to compensate. Other common cause is silicon contamination. A sensor may become contaminated after a vehicle repair procedure, if too much silicone sealant has been used. Some types of silicones are safe for oxygen sensors, though. Traces of this polymer can have an adverse effect after reaching and sticking to the tip of the O2 sensor.Whether the sensor has reached the end of its operating life or has been affected by contamination, the computer will alert the driver by turning on the check engine light or malfunction indicator light (MIL) on the dashboard. In either case, it is a good idea to replace the sensor and make any repairs, if necessary. It is easy to underestimate what an oxygen sensor does as a key component of anengine management system. However, an O2 sensor in good working order will help to keep vehicle emissions low, the engine working efficiently and fuel consumption under control.
