How does fuel band measure oxygen

Most sensors are manufactured with an integrated electrical heating element to sustain the response time at low exhaust temperatures.

This function assures that the emissions of the vehicle are controlled over a wider range of engine operating temperatures, especially during cold starts. There are two different types of oxygen sensors that differ in the output signal. The Narrowband Sensor operates in a narrow air-fuel ratio AFR region and produces a significant "jump" in the signal voltage around when the AFR goes higher than Lambda while the Wideband sensor provides a signal over a wider range for lambda.

Narrowband sensors are often just called oxygen sensors because for many years this was the only type of oxygen sensor available. It is called a narrow band sensor because it can only detect a very narrow range of AFRs. The function of this sensor is based on an electrochemical cell called a Nernst cell Figure 1. When the sensor is fitted, the outside of the Zirconia element is exposed to the exhaust gas and the inside is in contact with reference air. Both sides of the element are coated with thin layers of platinum that act as electrodes and carry the sensor voltage from the Zirconia element to the lead wires.

At operating temperature, oxygen ions are able to pass through the element and deposit charge on the platinum electrodes thus generating a voltage. It communicates with the ECU via the voltage it produces.

If the AFR is rich, a HIGH signal voltage is generated across the electrodes due to the difference in oxygen concentration present across the two sides of the element. Conversely, if the AFR is lean, a LOW voltage is generated across the electrodes due to the small difference in oxygen content between exhaust gases and the reference air inside the sensor.

Wideband sensors, also known as wide-range sensors, are a newer technology. A newer vehicle can report its emission monitor status during its current driving cycle. These monitors start from the beginning whenever the monitoring cycle meets the criteria to run a readiness test. Older cars might not support this feature. Because the monitors are a self-check routine that the driver does not have to initiate, the best way to get them ready to perform a self-test is to drive the vehicle.

There are a few requirements that vary from manufacturer to manufacturer. This allows the readiness monitors to go through their preset diagnostic routine. However, the following generic drive cycle usually works on most vehicles. Pre-plan a route that will allow you to bring the vehicle up to highway speeds and allow you to slow the vehicle down on a long coast. Advertisement Most drive cycles begin with a cold start, meaning the coolant and air temperatures are within 10 degrees of each another this condition can be achieved by letting the car to sit overnight.

The ignition key must be in the OFF position before the cold start. Otherwise, the heated oxygen sensor diagnostic may not run. Keep in mind, the non-continuous monitors may not catch a problem until the vehicle has been driven several times and the conditions are right to detect the fault.

Advertisement If one or more monitors are not ready, the vehicle will have to be driven under the correct conditions to make the monitor set. Then, and only then, will you get an accurate diagnosis. Fuel: Fuel Pressure And Volume.

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Advertise Subscribe Contact Us. By Andrew Markel. By Bob McDonald. By Brendan Baker Baker. Featured Video of the Week. Current Digital Issue Digital Edition. Sponsored Content. Newsletter Get the latest news, insights, and more delivered directly to you inbox. A sensing element sits inside the sensor, encased in a steel housing. On the other side of the nernst cell, oxygen from the air outside the exhaust travels down the O2 sensor and makes contact.

The difference in the amount of oxygen between that present in the outside air, and that present in the exhaust promotes the flow of oxygen ions and produces voltage. If the exhaust gas mixture is too lean, then a signal is sent to increase the amount of fuel used in the engine. Too much fuel produces hydrocarbons and carbon monoxide. Too little fuel produces nitrogen-oxide pollutants.

The sensor signal helps keep the mixture just right. Wide band O2 sensors have an additional O2 pumping cell to regulate the amount of oxygen present in the sensing element. Since the oxygen sensor is in the exhaust stream, it can become contaminated. Common sources of contamination include an excessively rich fuel mixture condition or oil blow-by in an older engine and engine coolant being burnt in the combustion chamber as a result of an engine gasket leak.

It is also exposed to extremely high temperatures, and like any component can wear over time. For this reason, there are a few tell-tale signs to look out for:. Before you replace the sensor, you need to diagnose the problem. Confirm the fault code by selecting live data and comparing the value of the suspect faulty sensor to that of a known working sensor. Other tooling or equipment may be required to determine if it is the actual sensor and not the wiring that is causing the problem.

How does an O2 sensor work? Why do O2 sensors fail?