What is an Oxygen Sensor?

The oxygen sensor, located in the exhaust system, determines the oxygen content of the exhaust gas. Since the amount of oxygen in the exhaust gas is a very good indictor of combustion efficiency, it is also the best place to monitor the air fuel ratio.

Question:
What is an oxygen sensor made of?

Answer:
An oxygen sensor is a solid electrolyte galvanic cell. Electrolyte is zirconium oxide, which is the same material synthetic diamonds are made from. This material is stabilized with a rare element called Yttria. The cell (thimble or flat plate) is then coated with pure platinum, which acts as a conductor/electrode (like battery plates).

Question:
How does the oxygen sensor work?

Answer:
The sensor works as a result of the varying quantities of oxygen in the exhaust verses the amount in the atmosphere. Voltage is produced by the difference in the two amounts. If the amount of oxygen in the exhaust is closer to the amount in the air, the engine is lean and the voltage is low (under 250mv). If the engine is rich the voltage is high (about 950mv).

Question:
What does an oxygen sensor do?

Answer:
The oxygen sensor monitors the engines air to fuel ratio by measuring the amount of free oxygen in the exhaust. It reports this information to the engine control unit or ECU. Approximately every 10 milliseconds the ECU uses this information to make corrections to the air to fuel mixture for maximum efficiency.

Question:
Are all oxygen base sensors generally the same?

Answer:
No. The base sensor design and elements vary greatly. Below is a list of the most widely used base sensors.

Question:
What is a universal sensor?

Answer:
A universal sensor is a base sensor, which does not include the direct fit connector. Splicing is necessary for installation. Universals were widely used in the early years of vehicles equipped with oxygen sensors.

The possibility exists that the user could select the wrong base sensor by assuming that all sensors with the same wire count are equal. All Oxygen Sensors are not created equally. Each type is matched to the make, model and sub-model application and cannot be mixed. It is impractical to offer a universal sensor for many applications due to heater types, ground types and other characteristics. Improper selection of the universal sensor could result in serious damage to the engine management system, including failure of the engine control unit (ECU) and/or the catalytic converter.

Question:
What will damage a sensor?

Answer:
Natural aging, shock from accidents, antifreeze poisoning, excessive oil consumption or leakage, silicone poisoning due
to incorrect use of silicone gasket sealers, etc.

Question:
How do I know if a sensor is damaged or not working properly?

Answer:
Usually the check engine light is illuminated if there is a failure of the sensor. Sensors that are not performing at peak efficiency may not cause the check engine light to illuminate, but will usually cause a rich shift in air fuel ratio and probably damage the catalyst.

Visual inspection will show signs of lead poisoning, antifreeze poisoning, silicone poisoning, and excessive oil consumption. When performing a vehicle tune up, remove the oxygen sensor and check for these common oxygen sensor conditions.

Question:
Where are oxygen sensors located and why?

Answer:
Oxygen sensors are located within the exhaust stream. There is at least one oxygen sensor located before the catalytic converter. Typically one in each exhaust manifold. These monitor the air fuel mixture of the engine. Depending on the exhaust design there is also one or two located after the catalytic converter to monitor its effectiveness.

Question:
How many oxygen sensors does my car have?

Answer:
If your car is fuel injected, there can be as many as eight sensors. You can find this information in the application guide
of our catalog.

Question:
What do wire colors mean?

Answer:
Typically the colors depict the connections inside the sensor; however, various manufacturers choose different colors. For example; some manufacturers use white wires for the heater & others use black. For this and many other reasons it is best to use a direct fit connector to avoid confusion.

Question:
How can I test my sensors?

Answer:
The best method is to use a scan tool and a portable DSO (Digital Storage Oscilloscope) to monitor the sensor switching characteristics. Connect the scan tool to the ALDL (assembly line diagnostics link) connector on the vehicle. This link allows you to monitor the performance of all sensors including the oxygen sensor. Inexpensive adapters that connect to a laptop or PDA (Personal Digital Assistant) allow you to use this method. Connect the DSO to the sensor leads to monitor its switching performance.

A second method is to connect some of the various testers available on the market directly to the oxygen sensor. This method is not as accurate, but can detect some of the sensor failures.

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