Oxygen sensor how does it work

When replacing an O2 sensor, make sure it is the same type as the original heated or unheated. Starting with a few vehicles in and , and all and newer vehicles, the number of oxygen sensors per engine has doubled.

A second oxygen sensor is now used downstream of the catalytic converter to monitor the converter's operating efficiency. On V6 or V8 engines with dual exhausts, this means up to four O2 sensors one for each cylinder bank and one after each converter may be used.

This includes keeping an eye on anything that might cause emissions to increase. The OBDII system compares the oxygen level readings of the O2 sensors before and after the converter to see if the converter is reducing the pollutants in the exhaust. If it sees little or no change in oxygen level readings, it means the converter is not working properly. O2 sensors are amazingly rugged considering the operating environment they live in.

But O2 sensors do wear out and eventually have to be replaced. The performance of the O2 sensor tends to diminish with age as contaminants accumulate on the sensor tip and gradually reduce its ability to produce voltage. This kind of deterioration can be caused by a variety of substances that find their way into the exhaust such as lead, silicone, sulfur, oil ash and even some fuel additives. The sensor can also be damaged by environmental factors such as water, splash from road salt, oil and dirt.

This happens because the flip-flopping of the fuel mixture is slowed down which reduces converter efficiency. The effect is more noticeable on engines with multiport fuel injection MFI than electronic carburetion or throttle body injection because the fuel ratio changes much more rapidly on MFI applications.

If the sensor dies altogether, the result can be a fixed, rich fuel mixture. Default on most fuel injected applications is mid-range after three minutes. This causes a big jump in fuel consumption as well as emissions.

And if the converter overheats because of the rich mixture, it may suffer damage. The only way to know if the O2 sensor is doing its job is to inspect it regularly.

That's why some vehicles mostly imports have a sensor maintenance reminder light. A good time to check the sensor is when the spark plugs are changed. You can read the O2 sensor's output with a scan tool or digital voltmeter, but the transitions are hard to see because the numbers jump around so much. Here's where a PC based scantool such as AutoTap really shines. You can use the graphing features to watch the transitions of the O2 sensors voltage.

The software will display the sensor's voltage output as a wavy line that shows both it's amplitude minimum and maximum voltage as well as its frequency transition rate from rich to lean. A good O2 sensor should produce an oscillating waveform at idle that makes voltage transitions from near minimum 0.

Making the fuel mixture artificially rich by feeding propane into the intake manifold should cause the sensor to respond almost immediately within milliseconds and go to maximum 0.

Creating a lean mixture by opening a vacuum line should cause the sensor's output to drop to its minimum 0. If the sensor doesn't flip-flop back and forth quickly enough, it may indicate a need for replacement. If the O2 sensor circuit opens, shorts or goes out of range, it may set a fault code and illuminate the Check Engine or Malfunction Indicator Lamp. If additional diagnosis reveals the sensor is defective, replacement is required.

But many O2 sensors that are badly degraded continue to work well enough not to set a fault code-but not well enough to prevent an increase in emissions and fuel consumption. I had a code for B1S1 but found a broken wire on another. The light stayed off but I still get crappy mileage.

Could it be still B1S1 or could it be upstream sensors? How do I know which sensor it is-can FIXD tell me so I can just tell mechanic to fix that one and they done rip me off?

Hey Crystal! Depending on which code the FIXD Sensor detects, it will tell you which specific sensor is having trouble. Hey does your fixd say upstream or downstream if its up its behind the motor if down its buy the cats but you may have more then too. Hi, my oxygen sensor lambda bank 1 sensor 1 value starts at 0. The mean value is 4. The part is located inside the intake tube, where the fresh air first comes into your engine.

That long plastic hose usually that connects to the throttle body. A delicate part though, so remove it carefully, On my 09 Mercury Marquis, it was two screws to loosen, then slide it out. Hope that helps. As another poster said-YouTube is wealth of informative videos for almost every car made.

Good luck! Your article is only partly correct. All it does is to complete combustion that may not have been completed in the engine. Oxygen sensor on Fords was only used as a redundant backup device to verify that the mixture control components were operating correctly. Check all air lines throughly check PCV valve as well that stopped alot of my check engine lights. I got a Jeep Grand Cherokee Laredo 3. Dual exhaust. How many O2 sensors would I have?

And what would I need to replace all of them? Hey I have a chevy malibu 1. Does anyone know where it is? I have p and p as codes and I want to clean the my oxygen sensor to see if that works. Thanks in advance for your help. I have a sensor before the catalytic converter which is O2 and then I have a sensor underneath the catalytic converter was wondering if I can keep it plugged in but gut the cat.

What would it mean then after replacing both o2 sensors and the cat, that the downstream is showing 1 volt at idle, but fluctuates up and down like the upstream during acceleration? BMW E93 i Both O2 sensors before cat are reading 2v. I guess I have to reduce richness somehow. O2 sensors after cat are reading 0. Your thoughts will be appreciated. Your email address will not be published. Save my name, email, and website in this browser for the next time I comment.

Share Share. Where are Oxygen Sensors Located? It provides a lambda value of 1 throughout various engine operating conditions. Besides, it compares the amount of oxygen in the exhaust gas against the amount of oxygen in the atmosphere. Read more: How does engine sensors work? CarBikeTech is a technical blog. Its members have an experience of over 20 years in the automobile field. CarBikeTech regularly publishes specific technical articles on automotive technology.

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