An oxygen (O2) sensor in the exhaust provides feedback to the PCM about:
- AIgnition timing advance
- BEngine oil level
- CThe air-fuel ratio (rich or lean)Correcta
- DCoolant temperature
Por qué: The oxygen sensor measures residual oxygen in the exhaust, telling the PCM whether the mixture is rich or lean so it can adjust fuel trim. A lazy or failed sensor degrades fuel control and emissions. Wide-band sensors report the actual ratio rather than just rich/lean.

