What does an oxygen sensor voltage reading of 0.0 - 0.3V indicate?

An oxygen sensor voltage reading of 0.0 - 0.3 volts typically indicates a lean fuel mixture. In this context, a lean mixture means that there is more air in relation to fuel in the combustion process, resulting in an insufficient amount of fuel for optimal combustion. When the engine runs lean, the oxygen sensor, which measures the amount of oxygen in the exhaust gases, produces a lower voltage output—often seen within this range.

Under normal operating conditions, a properly functioning oxygen sensor would oscillate between approximately 0.1 to 0.9 volts, indicating both rich and lean conditions as it responds to changes in the exhaust mixture. A reading at the lower end (0.0 to 0.3 volts) suggests that the engine is not getting enough fuel compared to the amount of air, thereby confirming the lean mixture condition.

It is important to consider that if an oxygen sensor is truly defective, it might produce erratic readings, potentially showing a voltage that is consistently low or high, but a reading at this specific range strongly correlates with a lean condition, rather than faulty sensor behavior.