What is the reason for the engine malfunction light being on but the car can still run normally?
4 Answers
The reason for the engine malfunction light being on but the car can still run normally is that the car needs maintenance such as an oil change. The engine malfunction light on the dashboard, usually red or yellow, will not automatically disappear in most cases once it lights up, though it may disappear on its own in rare instances. This is what is referred to as the engine malfunction light. If there is a current engine system fault, it should be checked and repaired promptly. Additionally, the fault information will be stored and provided as a reference to the car maintenance supervisor during repairs to resolve the issue more quickly. To ensure the engine can continue running when a fault occurs, if the detected fault has minimal impact on the engine's operation, the computer will ignore it. However, in reality, the engine is not in good working condition under such circumstances.
Yesterday my car's check engine light came on, but it drove fine otherwise. I asked a friend who knows about car repairs, and he said this is quite common, mostly due to sensor false alarms. For example, the oxygen sensor readings could be skewed by carbon buildup, or the fuel cap might not be tightened properly, causing fuel vapor leaks and triggering the system alarm. It could also be due to unstable battery voltage, causing the ECU to misjudge the fault. My friend said if this happens right after refueling, it's likely due to poor fuel quality. However, he also reminded me that while I can keep driving, I should read the trouble codes as soon as possible, as minor issues left unattended could eventually damage the catalytic converter.
When the engine light comes on but the car is still drivable, my advice is not to panic immediately. In 80% of cases, it's a minor component like a sensor acting up. Last time, I encountered carbon buildup in the throttle triggering the warning light, which disappeared after cleaning. Other issues like aging spark plugs or cracked ignition coils can also cause the system to misjudge—while these don't affect driving, they may increase fuel consumption. Some older cars with wiring degradation and poor contact can also report false faults. However, pay attention to the exhaust smell; if you detect gasoline odor or notice weakened power, it might indicate insufficient fuel pump pressure, in which case you should stop the car immediately for inspection.
With ten years of driving experience, I've encountered this situation three times—the car runs fine but the warning light stays on. The first check revealed dust on the air flow sensor, the second was a slightly clogged fuel injector, and the third was the simplest: the fuel cap wasn't tightened properly. The mechanic told me these minor issues won't cause an immediate breakdown but will put the engine into protection mode, increasing fuel consumption by up to 20%. He suggested trying an ECU reset first when this happens—disconnect the negative battery terminal for five minutes and then reconnect it—there's a one in three chance the fault code will clear itself.
