What does an oxygen sensor do?

Lou's Custom Exhaust - Tuesday, April 18, 2017

What Is An Oxygen Sensor? What Does It Do?


Oxygen Sensors, commonly referred to as O2 sensors, are part of your vehicles emission system. The purpose of the downstream, after converter, sensors is to monitor the quantities of harmful exhaust gases flowing into and out of the catalytic converter to ensure the converter is working properly.The sensor does not actually measure the amount of oxygen, but rather the difference between the amount of oxygen in the exhaust gas and the amount of oxygen in air.  There is also the upstream oxygen sensor which monitors the exhaust gasses to help the computer adjust your fuel/air ratio for maximum gas mileage and power.

Rich mixture (too much fuel) causes the sensors to demand oxygen. The demand for oxygen causes the internal circuit of the oxygen sensor to build voltage. Lean mixture (not enough fuel) causes low voltage. Modifying the signal that the oxygen sensor sends to the engine computer can damage the vehicle not to mention is extremely illegal and carries a hefty fine. When the engine is under a lower load such as slowing accelerating , or maintaining a constant speed, it is operating in closed loop mode.While in this mode your vehicles computer is basically anticipating your next move, assuming that you will be accelerating or decelerating . This loop forces the engine to operate both slightly lean and slightly rich. As the computer attempts to maintain a happy medium, If computer modifications have been done to the engine forcing it to run moderately lean, there will be a slight increase in fuel economy, usually at the expense of emissions, much higher exhaust gas temperatures, and an increase in power that can quickly turn into misfires and a drastic loss of power, as well as potential engine damage, at extremely lean air to fuel ratios.

If modifications cause the engine to run rich, there will be a slight increase in power to a point (the engine starts flooding from too much unburnt fuel) but at the cost of decreased fuel economy, and an increase in unburnt hydrocarbons in the exhaust which will basically turn your catalytic converters into a small furnace. Prolonged operation at rich mixtures can cause catastrophic failure of the catalytic converter. The ecu also controls the spark engine timing along with fuel injector pulse, so modifications which alter the engine to operate either too lean or too rich may also result in inefficient fuel consumption whenever fuel is ignited too soon or too late in the combustion cycle. A faulty O2 sensor can trigger a check engine light and also register as a failed catalytic converter, random cylinder misfires, camshaft/crankshaft positioning codes, and even transmission codes.Typically a replacement oxygen sensor can save you a lot of headaches and misdiagnosis. Poor fuel economy, stuttering engine, or a foul rotten egg smell? These are a few of the common symptoms of a bad oxygen sensor that if caught early enough can prevent more of the serious damages listed above.

At Lou’s Custom Exhaust of Hyannis, Plymouth, Quincy, and Westport we have the ability to read any check engine light and diagnose the cause to either a faulty sensor, catalytic converter, or any other emissions issue that may be related to the check engine light.

Give us a call if you would like a free estimate and a free check engine light diagnostic at any of our 4 locations:

Hyannis 508-771-2500
Plymouth 508-746-3500
Quincy 617-773-6500
Westport 508-646-1500

Share This