What symptom might indicate a faulty oxygen sensor?

A faulty oxygen sensor can significantly impact the vehicle's fuel management and overall engine performance. Oxygen sensors monitor the level of oxygen in the exhaust gases, providing critical information for the engine control unit (ECU) to adjust the air-fuel mixture for optimal combustion. When the oxygen sensor fails, it can lead to an incorrect air-fuel mixture, which often results in poor fuel economy due to excessive fuel usage. Additionally, the engine may run roughly because the wrong mixture can cause misfires, uneven idling, or increased emissions.

This symptom is key because it directly correlates to the sensor's function in regulating fuel efficiency and maintaining smooth engine operation. The other options do not specifically relate to the functions of the oxygen sensor; for example, high engine temperature might suggest a cooling system issue, while excessive oil consumption indicates problems related to engine wear or lubrication. Steering wheel vibrations typically stem from issues with wheel alignment or tire balance rather than the oxygen sensor's performance. Therefore, poor fuel economy and rough running are clear indicators of a malfunctioning oxygen sensor.