When observing an oxygen sensor voltage pattern that fluctuates from 0.25 volts to 0.8 volts, which technician is correct regarding the normalcy of the operation?

The observation of an oxygen sensor voltage pattern fluctuating between 0.25 volts and 0.8 volts indicates healthy sensor operation under closed loop conditions. In a properly functioning system, the voltage output of a typical oxygen sensor fluctuates within a specific range as the engine management system adjusts the air-fuel mixture for optimal combustion.

In closed loop operation, the sensor's voltage should oscillate between approximately 0.1 volts (lean) and 0.9 volts (rich), with a normal fluctuation occurring as the engine control unit (ECU) makes rapid adjustments to maintain the desired air-fuel ratio. The range observed, from 0.25 volts to 0.8 volts, falls within this operational pattern, suggesting that the oxygen sensor is actively responding to changes in the exhaust gases and the ECU is functioning properly.

This behavior indicates that the oxygen sensor is effectively relaying information to the ECU, allowing for the necessary adjustments to keep emissions within acceptable limits and maintain optimal engine performance. Therefore, the interpretation that this voltage pattern signifies normal closed loop operation is accurate.