What is a potential result of a malfunctioning oxygen sensor?

A malfunctioning oxygen sensor can lead to poor fuel economy and increased emissions because this component plays a critical role in the engine's air-fuel mixture management. The oxygen sensor monitors the level of oxygen in the exhaust gases, which helps the engine control module (ECM) adjust the fuel-air mixture for optimal combustion.

When the sensor fails, it may send incorrect data to the ECM, leading to an overly rich (too much fuel) or overly lean (too little fuel) mixture. An overly rich mixture causes excessive fuel consumption, resulting in poorer fuel economy as more fuel is burned than necessary. Additionally, this condition produces higher levels of unburned hydrocarbons in the exhaust, which increases emissions, contributing to environmental pollution and potentially causing the vehicle to fail emissions tests.

In contrast, a functioning oxygen sensor optimizes fuel efficiency and reduces harmful emissions by ensuring the correct air-fuel ratio is maintained during combustion. This highlights why the option related to poor fuel economy and increased emissions is indeed the correct result of a malfunctioning oxygen sensor.