500,000-mile Citroen Picasso! Is it sheer misery?

The oxygen (O2) sensor is a vital automotive component that monitors oxygen levels in exhaust gases to ensure the engine’s air-fuel mixture is optimal for efficient combustion and reduced emissions. Positioned in the exhaust manifold or pipe, it generates a voltage signal—low (~0.1V) for lean mixtures with excess oxygen, and high (~0.9V) for rich mixtures—feeding data to the ECU for real-time adjustments that boost fuel economy and cut pollutants like HC, CO, and NOx. A faulty O2 sensor triggers