How to Manually Reset the Car Malfunction Light?
2 Answers
Regardless of the reason for the engine malfunction light illuminating, after resolving the issue, it is necessary to use a computer to access the ECU program for resetting; there is no manual method to reset the malfunction light. Below are the reasons why the engine malfunction light may come on: 1. Poor quality, non-compliant gasoline. Most car owners have likely experienced this: shortly after refueling, the engine malfunction light appears on the dashboard. This is usually due to filling up with substandard gasoline at an unregulated gas station, leading to incomplete combustion of the air-fuel mixture during engine operation and triggering the malfunction light. While this does not affect driving safety, it can cause some degree of harm to the engine. 2. Oxygen sensor malfunction. Modern cars are equipped with two oxygen sensors, one before and one after the three-way catalytic converter. The front oxygen sensor detects the air-fuel ratio under different engine conditions, and the ECU adjusts fuel injection and calculates ignition timing based on this signal. The rear sensor primarily monitors the performance of the three-way catalytic converter. Therefore, if the oxygen sensor is damaged or its connector is faulty or loose, it can cause the air-fuel mixture to be too lean or too rich, triggering the malfunction light. 3. Mass air flow (MAF) sensor malfunction. The MAF sensor, also known as the air flow meter, measures the amount of air intake and converts it into an electrical signal sent to the ECU. Based on the optimal air-fuel ratio, the ECU determines the appropriate fuel injection amount. If the MAF sensor or its circuit malfunctions, the ECU cannot receive the correct air intake signal, leading to improper fuel control and resulting in a mixture that is too lean or too rich, causing the engine to malfunction. 4. Spark plug carbon buildup. The varying quality of fuel on the market and congested urban traffic make spark plugs prone to carbon buildup. Carbon deposits on spark plugs can cause poor engine performance, including difficulty starting, unstable idling, poor acceleration, backfiring during rapid acceleration, excessive exhaust emissions, and increased fuel consumption.
Manually clearing the fault light, I think the easiest way is to use an OBD scanner. There's a diagnostic port in the car, usually located under the steering wheel or near the engine hood. Plug in the scanner, start the vehicle, and the device will display the fault code. Once you confirm the issue is fixed, you can clear the light with one click. But don't mess around—if the oil light comes on, check the oil level first before clearing it, or you might damage the engine. I usually use a Bluetooth scanner that costs around a hundred yuan, paired with a mobile app for easy operation. There's also a makeshift method of disconnecting the battery negative terminal and waiting 5 minutes to reset, but that's not long-lasting and doesn't work for certain electrical faults. In short, investing in a good tool saves time and hassle.
