What causes three warning lights to appear when the car's power is turned on?
2 Answers
Three warning lights appearing when the car's power is turned on is due to the vehicle's onboard computer performing a self-check before starting. Below are the specific reasons why these lights remain on after the engine self-check is completed: Sensor malfunction: Includes coolant temperature, crankshaft position, air flow, intake air temperature, oxygen sensors, etc. When these sensors are damaged, have poor contact, or experience signal interruption, the car's ECU cannot accurately obtain engine data, triggering the engine warning light. Poor maintenance: Poor engine maintenance is the most common cause of the engine warning light illuminating. Vehicles have specific maintenance schedules, and if the owner fails to adhere to them, combined with poor driving habits, the engine's operational burden increases. Fuel and oil quality issues: This includes both fuel and engine oil. The fuel used in cars typically has a specific grade, and engine oil comes in semi-synthetic and fully synthetic varieties. If the owner does not use the required types, it can lead to engine wear over time. Poor combustion of the air-fuel mixture: Issues such as faulty spark plugs, ignition coil failure, fuel pump malfunction, or clogged fuel lines can cause poor combustion of the air-fuel mixture in the engine. This leads to engine carbon buildup or knocking problems, which are detected by the engine's oxygen sensors and reported to the ECU, resulting in the warning light illuminating as an alert.
Sometimes when I power on my car, three warning lights come on, such as the engine light, ABS light, and battery light. This usually happens because the car detects issues during its self-check process. If these lights remain on after the engine starts, it may indicate a fault. Common causes include: dirty or faulty sensors, like an ABS sensor covered in dust triggering false alarms; an aging battery or loose connections causing warning lights when power is insufficient; or minor glitches in the computer system. I once experienced this myself—it turned out my battery was failing, and the lights came on as soon as I powered the car. After replacing the battery, the issue was resolved. I recommend first observing whether the lights turn off after the engine starts. If they stay on, it's best to drive to a professional shop for a free diagnostic check—they can scan for trouble codes with their computer. Don’t ignore these warnings, as they may indicate safety hazards, such as brake system issues that could affect driving safety. Regular maintenance, including checking sensors and battery health, can prevent most of these problems. Overall, don’t panic—most cases are minor issues that can be resolved with timely attention.
