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Oxygen Sensor


Oxygen Sensor, also called the O2 sensor is an input sensor that reports to the ECU. It gives feedback and the air-fuel mixture burned by the engine. Usually, the exhaust system has two sensors. One is installed before the one installed after the catalytic converter. The O2 sensors are also responsible for the fuel economy of the car.

The oxygen sensor is installed in the exhaust manifold or exhaust pipe. It measures the amount of oxygen in the exhaust gas. The oxygen sensor is about the size of a spark plug and produces a small voltage when exposed to oxygen. This varying voltage is sent to the ECM. The voltage varies with the amount of oxygen in the exhaust gas.

  • During a closed-loop operation, the oxygen sensor reports to the ECM (Electronic Control Module).
  • If the oxygen content of the exhaust gas is high, the mixture is lean.
  • The ECM then shortens the pulse width so the spring keeps the plunger raised longer.
  • If the oxygen sensor reports that the oxygen content is low, the mixture is rich.
  • The ECM widens the pulse width to hold the plunger down longer, which closes the main well passage longer and makes the mixture lean.