Oxygen Sensor on Vehicles

Very important sensor as it regulates emissions and helps engine run as best as it can by controlling combustion at lambda 1 or 14.7 pieces of air to 1 piece of fuel. Its usually located on the top of exhaust manifold and operates at very high temperatures. The one we gonna test is Zirconia oxygen sensor with three wires, one is signal-white, 12 volts preheat power source-red and black as a ground.


Oxygen sensor pattern. Voltage varies from top 0.8 volts to bottom 0.1 volts. Average voltage is 0.45 volts almost lambda 1, 14.7 to 1 air fuel ratio.


Sudden acceleration makes the engine run rich and same as sudden deceleration makes it run lean.
Top ends of the oscilloscope graph is when O2 sensor showing rich and bottom end of the graph is when O2 sensor showing lean.
Also on this graph we can see that each square divided by 1 second and from that we can see sensor output changes from lean to rich and rich to lean at roughly in less then 100 milliseconds, 0.1 of a second.

This is a Zirconium oxygen sensor and it work effectively only when it red hot and around 300 degrees C, it produce voltage up to 1 volts when oxygen ions passes through the sensor relative to outside air. When air fuel mixture lean its it produce low voltage around 0.1 volts, but when mixture rich its produce up to 0.9 volts.

This sensor looks in very good condition as it cycles from rich 0.9 to lean 0.1 when car operates at constant 2500 RPM's, also it changes rich to lean reading in around 100 milliseconds.