Why is my Mercedes C-Class showing a check engine light with poor fuel efficiency?

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Why is my Mercedes C-Class showing a check engine light with poor fuel efficiency?

A check engine light combined with reduced fuel economy can indicate a catalytic converter problem, often related to inefficient emissions control. In Pakistan, where fuel quality can vary and EGR/PCV systems may get clogged, the catalytic converter can degrade over time. Faulty oxygen sensors o r improper combustion can also damage the converter, causing the cars computer to trigger the check engine light. A diagnostic scan can confirm if the converter efficiency is below threshold.

Talha Kyanii asked on 10 Oct 2025 18:15:53 pm

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Gari Master - on 10 Oct 2025 18:20:14 pm

When the catalytic converter starts to fail, it can no longer properly clean the exhaust gases, triggering the check engine light. In Pakistan, poor fuel, delayed oil changes, o r sensor issues especially with oxygen sensors can damage the converter over time. The car’s computer detects that emissions are not within normal range and activates the warning light. At the same time, the engine may compensate by adjusting fuel delivery, causing reduced fuel economy. A scan tool will usually show codes like P0420, indicating “Catalyst System Efficiency Below Threshold.”