What does a steady voltage reading of 0.8 volts from the front (upstream) oxygen sensor likely indicate?

A steady voltage reading of 0.8 volts from the front (upstream) oxygen sensor typically indicates that the engine is running rich. Oxygen sensors are designed to measure the level of oxygen in the exhaust gases. When the reading is around 0.8 volts, it typically signifies that there is a higher concentration of fuel compared to air in the combustion process.

In a rich condition, there is more fuel than the ideal air-fuel mixture, leading to an elevated voltage signal as the sensor responds to the excess fuel in the exhaust. This observation could prompt further diagnostics to identify why the engine is running rich, such as checking for fuel pressure issues, malfunctioning fuel injectors, or problems with the engine management system that may cause an incorrect fuel mixture.

Other options, while plausible under different conditions, do not align with a steady voltage of 0.8 volts from the oxygen sensor. A lean condition, for example, would generally result in a voltage reading lower than 0.5 volts, reflecting a higher air-to-fuel ratio. A faulty oxygen sensor might produce erratic or inconsistent readings rather than a steady voltage output. Lastly, while a failing catalytic converter may affect emissions readings, it wouldn’t directly cause the upstream sensor to