What Causes the Engine Warning Light to Intermittently Illuminate?

[Lorelei]

The reason is false error codes reported by sensors. During vehicle operation, the onboard computer detects no actual faults. After several ignition cycles and self-checks, the warning light automatically extinguishes. If communication between sensors and the computer is interrupted unexpectedly once or for a period, the computer may interpret this as a fault and illuminate the warning light. However, once communication is restored, the light will also turn off automatically after several ignition cycles. Causes of engine warning light illumination include: Poor-quality or substandard gasoline: Low-quality gasoline (e.g., containing excessive impurities, high gum content, or high sulfur levels) not only leads to incomplete combustion of the air-fuel mixture in the cylinders, resulting in excessive carbon deposits, but also poses risks such as clogging fuel lines and corroding components (e.g., fuel pumps). It also disrupts the normal air-fuel mixture ratio, ultimately triggering the engine warning light accompanied by shaking or vibration. Oxygen sensor malfunction: Most vehicles are equipped with two oxygen sensors, one before and one after the catalytic converter. The front oxygen sensor monitors the air-fuel ratio under different engine operating conditions, while the ECU uses this signal to adjust fuel injection and calculate ignition timing. The rear sensor primarily assesses the catalytic converter's performance. Therefore, if an oxygen sensor is damaged or its connector is faulty or loose, it may cause the air-fuel mixture to become too lean or rich, leading to the illumination of the warning light.