What is the normal voltage range for a properly working upstream oxygen sensor?

A properly functioning upstream oxygen sensor typically operates within the voltage range of 0.1V to 0.9V. This sensor is crucial in monitoring the oxygen levels in the exhaust gases as they exit the combustion chamber. When the engine is running, the oxygen sensor provides feedback to the engine control module (ECM), which then adjusts the air-fuel mixture to ensure optimal combustion and emissions control.

The lower end of the voltage range indicates a richer mixture (more fuel relative to air), while the higher end suggests a leaner mixture (more air relative to fuel). This range allows the vehicle's computer to make necessary adjustments to maintain efficient engine performance and reduce emissions. The specified range ensures that the sensor is responsive enough to provide accurate readings that the ECM can utilize effectively.

In contrast, the other options either provide voltage ranges that are too narrow or wide, which would not accurately reflect the performance of a typical upstream oxygen sensor.