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Difficulty: MediumExhaust and Emissions Systems

During closed-loop engine operation, the powertrain control module continuously adjusts the air-fuel ratio based on exhaust gas composition. Which exhaust system component is responsible for measuring the concentration of unburned oxygen in the exhaust stream?

  1. A
    Thermostat
  2. Oxygen sensorAnswer
  3. C
    Exhaust valve
  4. D
    Fuel pressure regulator

Answer

The oxygen sensor is the component responsible for measuring the concentration of unburned oxygen in the exhaust stream.
The oxygen sensor is installed in the exhaust manifold or exhaust pipe to measure the amount of oxygen remaining in the burnt gases. Its voltage output tells the engine computer whether the air-fuel mixture is rich (low oxygen) or lean (high oxygen), allowing precise adjustments to maintain optimum catalytic converter efficiency and low emissions.

Step-by-Step Solution

1
Identify the primary function required by the question
The target component must sample exhaust gases in real time and detect the amount of remaining oxygen.
Closed-loop feedback requires monitoring the combustion output to determine if the engine is running rich or lean.
2
Evaluate the roles of the available automotive components
The oxygen sensor (O2O_2 sensor) is mounted directly in the exhaust stream before and after the catalytic converter to measure oxygen content and signal the powertrain control module.
The other components govern cooling, mechanical gas expulsion, or fuel delivery pressure.

Key Concept

Oxygen Sensor Operation in Closed-Loop Engine Management
Estimated Time:1m 0s
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Topics

Exhaust and Emissions Systems

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