What causes the 'Focus engine fault, immediate inspection required' warning?

[Hernandez]

Possible reasons include poor fuel quality, engine malfunction, carbon buildup in the engine, or oxygen sensor issues. Below are detailed explanations: 1. Power: The vehicle delivers strong power with outstanding acceleration performance. The new Focus is equipped with an advanced powertrain system, featuring a 1.6L engine with variable valve timing that ensures smooth power delivery. 2. Voice system: The current Sync system was co-developed with Microsoft, but the touchscreen control system frequently experiences freezing, functional errors, and connection failures. Ford will collaborate with Canadian company BlackBerry Communications and adopt the QNX operating system. 3. Fuel: Using low-quality fuel in Focus vehicles can lead to incomplete combustion, potentially clogging the fuel filter screen. Prolonged use may damage spark plugs, catalytic converters, and oxygen sensors. Frequent low-speed urban driving in Focus vehicles tends to cause carbon buildup in the throttle body or engine internals. Extended driving periods may cause insulation layer degradation in high-pressure wires, making them prone to short circuits and triggering the 'engine fault, immediate inspection required' warning.