Chevrolet 12611127 Sensor Assembly, Heated Oxygen (Position 1)

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There is a galvanic battery called oxygen sensor that gives out a small voltage based on the amount of oxygen in the exhaust gases. A voltage change from stoichiometric 14.7:1 is needed by the catalyst for proper function. Motor vehicles whose engines are controlled by On-Board Diagnostics II (OBD-II) can confirm if the oxygen sensor and PCM feedback circuit are working correctly. Oxygen content level in the exhaust gas before and after catalytic converter can be used to determine it. The sensors upstream and downstream have heaters making them warm up quickly. It should be noted, though, that these sensors are very fragile and should be handled with extreme care as they can easily break when being serviced or replaced. In case of sensor replacement, it is important to start an engine within a short period to help remove old ones without damaging them further during removals. An upstream oxygen sensor can be screwed off with an oxygen socket and it lies on left side of the exhaust manifold while downstream one unscrews likewise using an oxygen socket located behind a catalytic converter. After removing sensors, any old sensor must be reused by applying anti-seize compound to ensure reinstallation of new sensors with already coated threads otherwise might also require application of anti-seize compounds as well.

When reinstalling the sensors, apply anti-seize compound to the threads if reusing the old sensor. Otherwise, new sensors already have anti-seize compounds on them.