A vehicle with CO₂ readings at 15.0% is likely suffering from what issue?

A vehicle with CO₂ readings at 15.0% indicates that the exhaust gas composition is not typical for normal operations. Elevated CO₂ levels usually suggest that the combustion process is not functioning optimally.

When the fuel mixture is too rich, it means there is an excessive amount of fuel relative to the air entering the combustion chamber. This leads to incomplete combustion as not all fuel is burned, resulting in an increase in carbon dioxide levels in the exhaust. In normal operating conditions, CO₂ levels would be significantly lower.

Therefore, in this scenario, a reading of 15.0% CO₂ is a strong indicator of a rich fuel mixture, as the engine is burning too much fuel compared to the amount of air, ultimately raising the CO₂ emissions. Understanding this relationship helps identify the underlying issues that may need addressing, such as adjusting the air-fuel mixture through tuning or diagnosing fuel system issues.