What causes the 'Engine Malfunction Service Required' warning in a Focus?

[Laura]

If the 'Engine Malfunction Service Required' warning appears in a Focus, it could be due to poor fuel quality, engine failure, carbon buildup in the engine, or issues with the oxygen sensor. The details are as follows: Fuel Quality: If a Focus frequently uses low-quality fuel, it can easily lead to incomplete combustion, causing the gasoline filter screen to clog. Prolonged use of such fuel can also damage the spark plugs, catalytic converter, and oxygen sensor. Carbon Buildup: If the Focus often drives at low speeds in urban areas, it can easily lead to carbon buildup in the throttle or inside the engine. When the vehicle has been driven for a long time, the insulation layer of the high-pressure wires may age and become prone to breakdown, which can also trigger the 'Engine Malfunction Service Required' warning.