How can you check for proper function of an oxygen sensor?

Monitoring the voltage output of an oxygen sensor during varying engine conditions is the best method to check for its proper function. Oxygen sensors are designed to provide feedback to the engine control module (ECM) about the oxygen content in the exhaust gases. This feedback is critical for the ECM to adjust the air-fuel mixture for optimal combustion.

When the engine is operating under different conditions—such as idle, acceleration, and deceleration—the oxygen sensor should produce a fluctuating voltage signal, typically ranging from about 0.1 volts (lean condition) to about 0.9 volts (rich condition). A healthy, functioning sensor will show these voltage variations in response to changes in the exhaust composition as it constantly adjusts the mixture to achieve efficient combustion.

This method allows a technician to not only verify that the sensor is functioning but also to understand how well the engine is performing under various load and operational conditions. Other methods, such as physical inspection or resistance checks, may indicate whether the sensor is damaged or disconnected, but they do not provide a comprehensive view of its operational effectiveness in real-time engine performance.